Patent Publication Number: US-9898371-B2

Title: Data storage system utilizing proxy device for storage operations

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 13/787,609, entitled DATA STORAGE SYSTEM UTILIZING PROXY DEVICE FOR STORAGE OPERATIONS, filed Mar. 6, 2013 which claims priority benefit to U.S. Provisional Application No. 61/607,728 entitled DATA STORAGE SYSTEM UTILIZING PROXY DEVICE FOR STORAGE OPERATIONS, filed Mar. 7, 2012, each of which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     Businesses worldwide recognize the commercial value of their data and seek reliable, cost-effective ways to protect the information stored on their computer networks while minimizing impact on productivity. Protecting information is often part of a routine process that is performed within an organization. 
     A company might back up critical computing systems such as databases, file servers, web servers, and so on as part of a daily, weekly, or monthly maintenance schedule. The company may similarly protect computing systems used by each of its employees, such as those used by an accounting department, marketing department, engineering department, and so forth. 
     Given the rapidly expanding volume of data under management, companies also continue to seek innovative techniques for managing data growth, in addition to protecting data. For instance, companies often implement migration techniques for moving data to lower cost storage over time and data reduction techniques for reducing redundant data, pruning lower priority data, etc. 
     Enterprises also increasingly view their stored data as a valuable asset. Along these lines, customers are looking for solutions that not only protect and manage, but also leverage their data. For instance, solutions providing data analysis capabilities, improved data presentation and access features, and the like, are in increasing demand. 
     In addition, many companies use virtualization techniques for a variety of purposes, such as to reduce the number of physical servers or other computers by instantiating multiple virtual machines on a single physical host computer. The term virtualization in the computing arts can refer to the creation of a virtual instance of an entity (e.g., a hardware platform, operating system, storage device or network resource, etc.) that behaves like a physical instance. For instance, a virtual machine can be a software representation of a physical machine. Virtualization can be used to centralize administrative tasks while improving scalability and workloads, and can be an important tool for maximizing hardware utilization. 
     Using virtualization techniques, many virtual machines (e.g., hundreds or thousands) can be instantiated on a single host device. The host device can contain significant amounts of memory and computing power in order to execute the virtual machines, which can be referred to as “clients” or “guests”. Although each virtual client can be logically viewed as a standalone device, in actuality the virtual client machines share underlying hardware with the other virtual machines residing on the host. 
     SUMMARY 
     In a virtualized system, or in any system where underlying storage media is shared by multiple clients, it can be challenging to effectively and securely administer the use of the storage media to service the storage needs of the various clients. This can be especially true for specialized storage operations, such as snapshot operations. 
     In view of the foregoing, a need exists for a system that can dynamically service storage requests from multiple client machines that share common underlying storage media. For instance, there is a need for systems and methods that service requests for access to underlying storage from multiple virtual clients residing on a single host device in a virtualized computing environment. For instance, in a virtualized computing environment, snapshots (e.g., hardware or software snapshots) of virtual machine data can be challenging to administer in a secure manner. 
     To address these challenges, certain embodiments described herein utilize a proxy machine to facilitate snapshots (or other storage operations) of data for virtual clients hosted by the proxy machine. A proxy mapping is kept for each of the clients, and as snapshot requests come in, the client consults the mapping and automatically routes the request to the appropriate proxy machine. The proxy machine then directs the storage device (e.g., hardware array) to perform the snapshot operation. The results of the operation can similarly be routed from the storage device to the proxy machine, and ultimately to the virtual client associated with the request. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a block diagram illustrating an exemplary information management system. 
         FIG. 1B  is a detailed view of a primary storage device, a secondary storage device, and some examples of primary data and secondary copy data. 
         FIG. 1C  is a block diagram of an exemplary information management system including a storage manager, one or more data agents, and one or more media agents. 
         FIG. 1D  is a block diagram illustrating a scalable information management system. 
         FIG. 1E  illustrates certain secondary copy operations according to an exemplary storage policy. 
         FIGS. 2A-2C  are block diagrams illustrative of embodiments of a storage network environment including a proxy client communicating with a storage device on behalf of a client. 
         FIGS. 3A and 3B  are state diagrams illustrative of the interaction between the various components of the storage network environment of  FIG. 2A . 
         FIGS. 4-7  are flow diagrams illustrative of embodiments of routines implemented by a client proxy for requesting a storage device to perform one or more storage operations on behalf of a client. 
     
    
    
     DETAILED DESCRIPTION 
     Generally described, the present disclosure is directed to a system, method, and computer readable non-transitory storage medium for a storage management system. Specifically, embodiments described herein include systems and methods for servicing requests to perform storage on client data, where multiple clients share underlying storage media. The requests, as well as the results of the storage operations, are routed through a proxy, which interfaces with the storage media. The proxy may be a physical host in a virtualized computing environment or may be implemented on a host in a virtualized computing environment. And the clients may be physical clients, or virtual clients instantiated on the host. In other cases, the proxy and the clients are implemented on separate computing devices. Furthermore, the clients may not have direct access to the hardware array or other storage device. In some embodiments, for example, the clients cannot perform one or more types of storage operations (e.g., snapshot operations) without the aid of the proxy. In some embodiments, the clients only communicate with and/or access the storage device via the proxy. 
     As an example, and not to be construed as limiting, the storage manager can contain a storage policy that determines how frequently a snapshot is taken of the client and the proxy client, how and when data is to be reverted, etc. Based on the storage policy, the storage manager transmits a storage operation request to the client. The client, recognizing that it is unable to perform the storage operation request, requests that the proxy client perform the storage operation request. The proxy client receives the storage operation request and identifies the portions of hardware storage that contain the data associated with the client. The proxy client then transmits the storage operation request to the storage device, specifying the portions of hardware storage that contain the data associated with the client. 
     The storage device performs the requested storage operation on the specified portions of hardware storage and notifies the proxy client upon completion. The notification can include, but is not limited to a snapshot identifier, a disk array identifier, or other information related to the snapshot. Upon receiving the notification from the storage device, the proxy client transmits relevant data to the client. The client can then notify the storage manager that the storage operation has been completed. 
     In some embodiments, the storage operation is a snapshot creation. Accordingly, the storage manager transmits a snapshot command based on a storage policy to the client. Upon receiving the command and determining that the client is unable to create the snapshot, the client transmits a snapshot creation request to the proxy client. The client identifies the portions of physical storage in the disk array that contain the data associated with the client. The proxy client transmits the snapshot creation request to the storage device, identifying the portions of physical storage in the disk array that are to form part of the snapshot. Upon creating the snapshot, the storage device transmits to the client a snapshot identifier, and other information. For example, the storage device can transmit a volume snap identifier, a group identifier, the status of the device, creation time, and/or an array identifier. The proxy client transmits a snapshot identifier to the client, and the client notifies the storage manager that the snapshot has been created. 
     In certain embodiments the storage operation can be a mount or read of a snapshot. In such an embodiment the storage manager transmits a mount/read command of a particular snapshot to the client. Upon receiving the command, the client determines whether the client is able to mount the particular snapshot. If the client does not have access to the storage device or is otherwise unable to mount the particular snapshot directly, the client requests the proxy client to map the portions of the storage device that contain the snapshot data to the client. In the request, the client can include the snapshot identifier. The proxy client communicates with the storage device to identify the portions of physical storage in the disk array that contain the data associated with the client, including the particular snapshot. The proxy client requests location identifying information of the portions of physical storage from the disk array that contain the particular snapshot, and the storage device retrieves the location identifying information, or snapshot disk data. The proxy client in turn transmits the snapshot disk data to the client. Upon receiving the snapshot location information and/or disk data, the client can mount the snapshot and notify the storage manager of the completion of the mounting. Once mounted, the client can access the snap mounted disk directly. 
     In some embodiments, the storage operation is a snapshot revert operation, where the snapshot is accessed to revert the virtual client data store back to the state it was in at the time the snapshot was taken. In such an embodiment, the storage manager transmits a revert command to the client to revert to a specified snapshot. The client determines that it cannot perform the revert operation alone and transmits the reversion request to the proxy client, such as the agent of the proxy client. The reversion request can include information uniquely identifying the specified snapshot, such as location information, other disk data and/or a snapshot identifier, etc. The proxy client transmits the request for the reversion to the storage device. The storage device uses the information received from the proxy client to revert to an earlier snapshot version of the data related to the requesting client. Once the storage device has completed the reversion, the storage device notifies the proxy client and the proxy client notifies the client. In turn, the client notifies the storage manager of the completion of the reversion. 
     Information Management System Overview 
     With the increasing importance of protecting and leveraging data, organizations simply cannot afford to take the risk of losing critical data. Moreover, runaway data growth and other modern realities make protecting and managing data an increasingly difficult task. There is therefore a need for efficient, powerful, and user-friendly solutions for protecting and managing data. 
     Depending on the size of the organization, there are typically many data production sources which are under the purview of tens, hundreds, or even thousands of employees or other individuals. In the past, individual employees were sometimes responsible for managing and protecting their data. A patchwork of hardware and software point solutions have been applied in other cases. These solutions were often provided by different vendors and had limited or no interoperability. 
     Certain embodiments described herein provide systems and methods capable of addressing these and other shortcomings of prior approaches by implementing unified, organization-wide information management.  FIG. 1A  shows one such information management system  100 , which generally includes combinations of hardware and software configured to protect and manage data and metadata generated and used by the various computing devices in the information management system  100 . 
     The organization which employs the information management system  100  may be a corporation or other business entity, non-profit organization, educational institution, household, governmental agency, or the like. 
     Generally, the systems and associated components described herein may be compatible with and/or provide some or all of the functionality of the systems and corresponding components described in one or more of the following U.S. patents and patent application publications assigned to CommVault Systems, Inc., each of which is hereby incorporated in its entirety by reference herein:
         U.S. Pat. Pub. No. 2010-0332456, entitled “DATA OBJECT STORE AND SERVER FOR A CLOUD STORAGE ENVIRONMENT, INCLUDING DATA DEDUPLICATION AND DATA MANAGEMENT ACROSS MULTIPLE CLOUD STORAGE SITES”;   U.S. Pat. No. 7,035,880, entitled “MODULAR BACKUP AND RETRIEVAL SYSTEM USED IN CONJUNCTION WITH A STORAGE AREA NETWORK”;   U.S. Pat. No. 7,343,453, entitled “HIERARCHICAL SYSTEMS AND METHODS FOR PROVIDING A UNIFIED VIEW OF STORAGE INFORMATION”;   U.S. Pat. No. 7,395,282, entitled “HIERARCHICAL BACKUP AND RETRIEVAL SYSTEM”;   U.S. Pat. No. 7,246,207, entitled “SYSTEM AND METHOD FOR DYNAMICALLY PERFORMING STORAGE OPERATIONS IN A COMPUTER NETWORK”;   U.S. Pat. No. 7,747,579, entitled “METABASE FOR FACILITATING DATA CLASSIFICATION”;   U.S. Pat. No. 8,229,954, entitled “MANAGING COPIES OF DATA”;   U.S. Pat. No. 7,617,262, entitled “SYSTEM AND METHODS FOR MONITORING APPLICATION DATA IN A DATA REPLICATION SYSTEM”;   U.S. Pat. No. 7,529,782, entitled “SYSTEM AND METHODS FOR PERFORMING A SNAPSHOT AND FOR RESTORING DATA”;   U.S. Pat. No. 8,230,195, entitled “SYSTEM AND METHOD FOR PERFORMING AUXILIARY STORAGE OPERATIONS”;   U.S. Pat. No. 8,364,652, entitled “CONTENT-ALIGNED, BLOCK-BASED DEDUPLICATION”;   U.S. Pat. Pub. No. 2006/0224846, entitled “SYSTEM AND METHOD TO SUPPORT SINGLE INSTANCE STORAGE OPERATIONS”;   U.S. Pat. Pub. No. 2009/0329534, entitled “APPLICATION-AWARE AND REMOTE SINGLE INSTANCE DATA MANAGEMENT”;   U.S. Pat. Pub. No. 2012/0150826, entitled “DISTRIBUTED DEDUPLICATED STORAGE SYSTEM”;   U.S. Pat. Pub. No. 2012/0150818, entitled “CLIENT-SIDE REPOSITORY IN A NETWORKED DEDUPLICATED STORAGE SYSTEM”;   U.S. Pat. No. 8,170,995, entitled “METHOD AND SYSTEM FOR OFFLINE INDEXING OF CONTENT AND CLASSIFYING STORED DATA”; and   U.S. Pat. No. 8,156,086, entitled “SYSTEMS AND METHODS FOR STORED DATA VERIFICATION”.       

     The illustrated information management system  100  includes one or more client computing device  102  having at least one application  110  executing thereon, and one or more primary storage devices  104  storing primary data  112 . The client computing device(s)  102  and the primary storage devices  104  may generally be referred to in some cases as a primary storage subsystem  117 . 
     Depending on the context, the term “information management system” can refer to generally all of the illustrated hardware and software components. Or, in other instances, the term may refer to only a subset of the illustrated components. 
     For instance, in some cases information management system  100  generally refers to a combination of specialized components used to protect, move, manage, manipulate and/or process data and metadata generated by the client computing devices  102 . However, the term may generally not refer to the underlying components that generate and/or store the primary data  112 , such as the client computing devices  102  themselves, the applications  110  and operating system residing on the client computing devices  102 , and the primary storage devices  104 . 
     As an example, “information management system” may sometimes refer only to one or more of the following components and corresponding data structures: storage managers, data agents, and media agents. These components will be described in further detail below. 
     Client Computing Devices 
     There are typically a variety of sources in an organization that produce data to be protected and managed. As just one illustrative example, in a corporate environment such data sources can be employee workstations and company servers such as a mail server, a web server, or the like. In the information management system  100 , the data generation sources include the one or more client computing devices  102 . 
     The client computing devices  102  may include, without limitation, one or more: workstations, personal computers, desktop computers, or other types of generally fixed computing systems such as mainframe computers and minicomputers. 
     The client computing devices  102  can also include mobile or portable computing devices, such as one or more laptops, tablet computers, personal data assistants, mobile phones (such as smartphones), and other mobile or portable computing devices such as embedded computers, set top boxes, vehicle-mounted devices, wearable computers, etc. 
     In some cases, each client computing device  102  is associated with one or more users and/or corresponding user accounts, of employees or other individuals. 
     The term “client computing device” is used herein because the information management system  100  generally “serves” the data management and protection needs for the data generated by the client computing devices  102 . However, the use of this term does not imply that the client computing devices  102  cannot be “servers” in other respects. For instance, a particular client computing device  102  may act as a server with respect to other devices, such as other client computing devices  102 . As just a few examples, the client computing devices  102  can include mail servers, file servers, database servers, and web servers. 
     The client computing devices  102  may additionally include virtualized and/or cloud computing resources. For instance, one or more virtual machines may be provided to the organization by a third-party cloud service vendor. Or, in some embodiments, the client computing devices  102  include one or more virtual machine(s) running on a virtual machine host computing device operated by the organization. As one example, the organization may use one virtual machine as a database server and another virtual machine as a mail server. A virtual machine manager (VMM) (e.g., a Hypervisor) may manage the virtual machines, and reside and execute on the virtual machine host computing device. 
     Each client computing device  102  may have one or more applications  110  (e.g., software applications) executing thereon which generate and manipulate the data that is to be protected from loss. 
     The applications  110  generally facilitate the operations of an organization (or multiple affiliated organizations), and can include, without limitation, mail server applications (e.g., Microsoft Exchange Server), file server applications, mail client applications (e.g., Microsoft Exchange Client), database applications (e.g., SQL, Oracle, SAP, Lotus Notes Database), word processing applications (e.g., Microsoft Word), spreadsheet applications, financial applications, presentation applications, browser applications, mobile applications, entertainment applications, and so on. 
     The applications  110  can include at least one operating system (e.g., Microsoft Windows, Mac OS X, iOS, IBM z/OS, Linux, other Unix-based operating systems, etc.), which may support one or more file systems and host the other applications  110 . 
     As shown, the client computing devices  102  and other components in the information management system  100  can be connected to one another via one or more communication pathways  114 . The communication pathways  114  can include one or more networks or other connection types including as any of following, without limitation: the Internet, a wide area network (WAN), a local area network (LAN), a Storage Area Network (SAN), a Fibre Channel connection, a Small Computer System Interface (SCSI) connection, a virtual private network (VPN), a token ring or TCP/IP based network, an intranet network, a point-to-point link, a cellular network, a wireless data transmission system, a two-way cable system, an interactive kiosk network, a satellite network, a broadband network, a baseband network, other appropriate wired, wireless, or partially wired/wireless computer or telecommunications networks, combinations of the same or the like. The communication pathways  114  in some cases may also include application programming interfaces (APIs) including, e.g., cloud service provider APIs, virtual machine management APIs, and hosted service provider APIs. 
     Primary Data and Exemplary Primary Storage Devices 
     Primary data  112  according to some embodiments is production data or other “live” data generated by the operating system and other applications  110  residing on a client computing device  102 . The primary data  112  is stored on the primary storage device(s)  104  and is organized via a file system supported by the client computing device  102 . For instance, the client computing device(s)  102  and corresponding applications  110  may create, access, modify, write, delete, and otherwise use primary data  112 . 
     Primary data  112  is generally in the native format of the source application  110 . According to certain aspects, primary data  112  is an initial or first (e.g., created before any other copies or before at least one other copy) stored copy of data generated by the source application  110 . Primary data  112  in some cases is created substantially directly from data generated by the corresponding source applications  110 . 
     The primary data  112  may sometimes be referred to as a “primary copy” in the sense that it is a discrete set of data. However, the use of this term does not necessarily imply that the “primary copy” is a copy in the sense that it was copied or otherwise derived from another stored version. 
     The primary storage devices  104  storing the primary data  112  may be relatively fast and/or expensive (e.g., a disk drive, a hard-disk array, solid state memory, etc.). In addition, primary data  112  may be intended for relatively short term retention (e.g., several hours, days, or weeks). 
     According to some embodiments, the client computing device  102  can access primary data  112  from the primary storage device  104  by making conventional file system calls via the operating system. Primary data  112  representing files may include structured data (e.g., database files), unstructured data (e.g., documents), and/or semi-structured data. Some specific examples are described below with respect to  FIG. 1B . 
     It can be useful in performing certain tasks to break the primary data  112  up into units of different granularities. In general, primary data  112  can include files, directories, file system volumes, data blocks, extents, or any other types or granularities of data objects. As used herein, a “data object” can refer to both (1) any file that is currently addressable by a file system or that was previously addressable by the file system (e.g., an archive file) and (2) a subset of such a file. 
     As will be described in further detail, it can also be useful in performing certain functions of the information management system  100  to access and modify metadata within the primary data  112 . Metadata generally includes information about data objects or characteristics associated with the data objects. 
     Metadata can include, without limitation, one or more of the following: the data owner (e.g., the client or user that generates the data), the last modified time (e.g., the time of the most recent modification of the data object), a data object name (e.g., a file name), a data object size (e.g., a number of bytes of data), information about the content (e.g., an indication as to the existence of a particular search term), to/from information for email (e.g., an email sender, recipient, etc.), creation date, file type (e.g., format or application type), last accessed time, application type (e.g., type of application that generated the data object), location/network (e.g., a current, past or future location of the data object and network pathways to/from the data object), frequency of change (e.g., a period in which the data object is modified), business unit (e.g., a group or department that generates, manages or is otherwise associated with the data object), and aging information (e.g., a schedule, such as a time period, in which the data object is migrated to secondary or long term storage), boot sectors, partition layouts, file location within a file folder directory structure, user permissions, owners, groups, access control lists [ACLs]), system metadata (e.g., registry information), combinations of the same or the like. 
     In addition to metadata generated by or related to file systems and operating systems, some of the applications  110  maintain indices of metadata for data objects, e.g., metadata associated with individual email messages. Thus, each data object may be associated with corresponding metadata. The use of metadata to perform classification and other functions is described in greater detail below. 
     Each of the client computing devices  102  are associated with and/or in communication with one or more of the primary storage devices  104  storing corresponding primary data  112 . A client computing device  102  may be considered to be “associated with” or “in communication with” a primary storage device  104  if it is capable of one or more of: storing data to the primary storage device  104 , retrieving data from the primary storage device  104 , and modifying data retrieved from a primary storage device  104 . 
     The primary storage devices  104  can include, without limitation, disk drives, hard-disk arrays, semiconductor memory (e.g., solid state drives), and network attached storage (NAS) devices. In some cases, the primary storage devices  104  form part of a distributed file system. The primary storage devices  104  may have relatively fast I/O times and/or are relatively expensive in comparison to the secondary storage devices  108 . For example, the information management system  100  may generally regularly access data and metadata stored on primary storage devices  104 , whereas data and metadata stored on the secondary storage devices  108  is accessed relatively less frequently. 
     In some cases, each primary storage device  104  is dedicated to an associated client computing devices  102 . For instance, a primary storage device  104  in one embodiment is a local disk drive of a corresponding client computing device  102 . In other cases, one or more primary storage devices  104  can be shared by multiple client computing devices  102 . As one example, a primary storage device  104  can be a disk array shared by a group of client computing devices  102 , such as one of the following types of disk arrays: EMC Clariion, EMC Symmetrix, EMC Celerra, Dell EqualLogic, IBM XIV, NetApp FAS, HP EVA, and HP 3PAR. 
     The information management system  100  may also include hosted services (not shown), which may be hosted in some cases by an entity other than the organization that employs the other components of the information management system  100 . For instance, the hosted services may be provided by various online service providers to the organization. Such service providers can provide services including social networking services, hosted email services, or hosted productivity applications or other hosted applications). 
     Hosted services may include software-as-a-service (SaaS), platform-as-a-service (PaaS), application service providers (ASPs), cloud services, or other mechanisms for delivering functionality via a network. As it provides services to users, each hosted service may generate additional data and metadata under management of the information management system  100 , e.g., as primary data  112 . In some cases, the hosted services may be accessed using one of the applications  110 . As an example, a hosted mail service may be accessed via browser running on a client computing device  102 . 
     Secondary Copies and Exemplary Secondary Storage Devices 
     The primary data  112  stored on the primary storage devices  104  may be compromised in some cases, such as when an employee deliberately or accidentally deletes or overwrites primary data  112  during their normal course of work. Or the primary storage devices  104  can be damaged or otherwise corrupted. 
     For recovery and/or regulatory compliance purposes, it is therefore useful to generate copies of the primary data  112 . Accordingly, the information management system  100  includes one or more secondary storage computing devices  106  and one or more secondary storage devices  108  configured to create and store one or more secondary copies  116  of the primary data  112  and associated metadata. The secondary storage computing devices  106  and the secondary storage devices  108  may be referred to in some cases as a secondary storage subsystem  118 . 
     Creation of secondary copies  116  can help meet information management goals, such as: restoring data and/or metadata if an original version (e.g., of primary data  112 ) is lost (e.g., by deletion, corruption, or disaster); allowing point-in-time recovery; complying with regulatory data retention and electronic discovery (e-discovery) requirements; reducing utilized storage capacity; facilitating organization and search of data; improving user access to data files across multiple computing devices and/or hosted services; and implementing data retention policies. 
     Types of secondary copy operations can include, without limitation, backup operations, archive operations, snapshot operations, replication operations (e.g., continuous data replication [CDR]), data retention policies such as information lifecycle management and hierarchical storage management operations, and the like. These specific types operations are discussed in greater detail below. 
     Regardless of the type of secondary copy operation, the client computing devices  102  access or receive primary data  112  and communicate the data, e.g., over the communication pathways  114 , for storage in the secondary storage device(s)  108 . 
     A secondary copy  116  can comprise a separate stored copy of application data that is derived from one or more earlier created, stored copies (e.g., derived from primary data  112  or another secondary copy  116 ). Secondary copies  116  can include point-in-time data, and may be intended for relatively long-term retention (e.g., weeks, months or years), before some or all of the data is moved to other storage or is discarded. 
     In some cases, a secondary copy  116  is a copy of application data created and stored subsequent to at least one other stored instance (e.g., subsequent to corresponding primary data  112  or to another secondary copy  116 ), in a different storage device than at least one previous stored copy, and/or remotely from at least one previous stored copy. Secondary copies  116  may be stored in relatively slow and/or low cost storage (e.g., magnetic tape). A secondary copy  116  may be stored in a backup or archive format, or in some other format different than the native source application format or other primary data format. 
     In some cases, secondary copies  116  are indexed so users can browse and restore at another point in time. After creation of a secondary copy  116  representative of certain primary data  112 , a pointer or other location indicia (e.g., a stub) may be placed in primary data  112 , or be otherwise associated with primary data  112  to indicate the current location on the secondary storage device(s)  108 . 
     Since an instance a data object or metadata in primary data  112  may change over time as it is modified by an application  110  (or hosted service or the operating system), the information management system  100  may create and manage multiple secondary copies  116  of a particular data object or metadata, each representing the state of the data object in primary data  112  at a particular point in time. Moreover, since an instance of a data object in primary data  112  may eventually be deleted from the primary storage device  104  and the file system, the information management system  100  may continue to manage point-in-time representations of that data object, even though the instance in primary data  112  no longer exists. 
     For virtualized computing devices the operating system and other applications  110  of the client computing device(s)  102  may execute within or under the management of virtualization software (e.g., a VMM), and the primary storage device(s)  104  may comprise a virtual disk created on a physical storage device. The information management system  100  may create secondary copies  116  of the files or other data objects in a virtual disk file and/or secondary copies  116  of the entire virtual disk file itself (e.g., of an entire .vmdk file). 
     Secondary copies  116  may be distinguished from corresponding primary data  112  in a variety of ways, some of which will now be described. First, as discussed, secondary copies  116  can be stored in a different format (e.g., backup, archive, or other non-native format) than primary data  112 . For this or other reasons, secondary copies  116  may not be directly useable by the applications  110  of the client computing device  102 , e.g., via standard system calls or otherwise without modification, processing, or other intervention by the information management system  100 . 
     Secondary copies  116  are also often stored on a secondary storage device  108  that is inaccessible to the applications  110  running on the client computing devices  102  (and/or hosted services). Some secondary copies  116  may be “offline copies,” in that they are not readily available (e.g. not mounted to tape or disk). Offline copies can include copies of data that the information management system  100  can access without human intervention (e.g. tapes within an automated tape library, but not yet mounted in a drive), and copies that the information management system  100  can access only with at least some human intervention (e.g. tapes located at an offsite storage site). 
     The secondary storage devices  108  can include any suitable type of storage device such as, without limitation, one or more tape libraries, disk drives or other magnetic, non-tape storage devices, optical media storage devices, solid state storage devices, NAS devices, combinations of the same, and the like. In some cases, the secondary storage devices  108  are provided in a cloud (e.g. a private cloud or one operated by a third-party vendor). 
     The secondary storage device(s)  108  in some cases comprises a disk array or a portion thereof. In some cases, a single storage device (e.g., a disk array) is used for storing both primary data  112  and at least some secondary copies  116 . In one example, a disk array capable of performing hardware snapshots stores primary data  112  and creates and stores hardware snapshots of the primary data  112  as secondary copies  116 . 
     The Use of Intermediary Devices for Creating Secondary Copies 
     Creating secondary copies can be a challenging task. For instance, there can be hundreds or thousands of client computing devices  102  continually generating large volumes of primary data  112  to be protected. Also, there can be significant overhead involved in the creation of secondary copies  116 . Moreover, secondary storage devices  108  may be special purpose components, and interacting with them can require specialized intelligence. 
     In some cases, the client computing devices  102  interact directly with the secondary storage device  108  to create the secondary copies  116 . However, in view of the factors described above, this approach can negatively impact the ability of the client computing devices  102  to serve the applications  110  and produce primary data  112 . Further, the client computing devices  102  may not be optimized for interaction with the secondary storage devices  108 . 
     Thus, in some embodiments, the information management system  100  includes one or more software and/or hardware components which generally act as intermediaries between the client computing devices  102  and the secondary storage devices  108 . In addition to off-loading certain responsibilities from the client computing devices  102 , these intermediary components can provide other benefits. For instance, as discussed further below with respect to  FIG. 1D , distributing some of the work involved in creating secondary copies  116  can enhance scalability. 
     The intermediary components can include one or more secondary storage computing devices  106  as shown in  FIG. 1A  and/or one or more media agents, which can be software modules residing on corresponding secondary storage computing devices  106  (or other appropriate devices). Media agents are discussed below (e.g., with respect to  FIGS. 1C-1E ). 
     The secondary storage computing device(s)  106  can comprise any appropriate type of computing device and can include, without limitation, any of the types of fixed and portable computing devices described above with respect to the client computing devices  102 . In some cases, the secondary storage computing device(s)  106  include specialized hardware and/or software componentry for interacting with the secondary storage devices  108 . 
     To create a secondary copy  116 , the client computing device  102  communicates the primary data  112  to be copied (or a processed version thereof) to the designated secondary storage computing device  106 , via the communication pathway  114 . The secondary storage computing device  106  in turn conveys the received data (or a processed version thereof) to the secondary storage device  108 . In some such configurations, the communication pathway  114  between the client computing device  102  and the secondary storage computing device  106  comprises a portion of a LAN, WAN or SAN. In other cases, at least some client computing devices  102  communicate directly with the secondary storage devices  108  (e.g., via Fibre Channel or SCSI connections). 
     Exemplary Primary Data and an Exemplary Secondary Copy 
       FIG. 1B  is a detailed view showing some specific examples of primary data stored on the primary storage device(s)  104  and secondary copy data stored on the secondary storage device(s)  108 , with other components in the system removed for the purposes of illustration. Stored on the primary storage device(s)  104  are primary data objects including word processing documents  119 A-B, spreadsheets  120 , presentation documents  122 , video files  124 , image files  126 , email mailboxes  128  (and corresponding email messages  129 A-C), html/xml or other types of markup language files  130 , databases  132  and corresponding tables  133 A- 133 C). 
     Some or all primary data objects are associated with a primary copy of object metadata (e.g., “Meta1-11”), which may be file system metadata and/or application specific metadata. Stored on the secondary storage device(s)  108  are secondary copy objects  134 A-C which may include copies of or otherwise represent corresponding primary data objects and metadata. 
     As shown, the secondary copy objects  134 A-C can individually represent more than one primary data object. For example, secondary copy data object  134 A represents three separate primary data objects  133 C,  122  and  129 C (represented as  133 C′,  122 ′ and  129 C′, respectively). Moreover, as indicated by the prime mark (′), a secondary copy object may store a representation of a primary data object or metadata differently than the original format, e.g., in a compressed, encrypted, deduplicated, or other modified format. 
     Exemplary Information Management System Architecture 
     The information management system  100  can incorporate a variety of different hardware and software components, which can in turn be organized with respect to one another in many different configurations, depending on the embodiment. There are critical design choices involved in specifying the functional responsibilities of the components and the role of each component in the information management system  100 . For instance, as will be discussed, such design choices can impact performance as well as the adaptability of the information management system  100  to data growth or other changing circumstances. 
       FIG. 1C  shows an information management system  100  designed according to these considerations and which includes: a central storage or information manager  140  configured to perform certain control functions, one or more data agents  142  executing on the client computing device(s)  102  configured to process primary data  112 , and one or more media agents  144  executing on the one or more secondary storage computing devices  106  for performing tasks involving the secondary storage devices  108 . 
     Storage Manager 
     As noted, the number of components in the information management system  100  and the amount of data under management can be quite large. Managing the components and data is therefore a significant task, and a task that can grow in an often unpredictable fashion as the quantity of components and data scale to meet the needs of the organization. 
     For these and other reasons, according to certain embodiments, responsibility for controlling the information management system  100 , or at least a significant portion of that responsibility, is allocated to the storage manager  140 . 
     By distributing control functionality in this manner, the storage manager  140  can be adapted independently according to changing circumstances. Moreover, a host computing device can be selected to best suit the functions of the storage manager  140 . These and other advantages are described in further detail below with respect to  FIG. 1D . 
     The storage manager  140  may be a software module or other application. The storage manager generally initiates, coordinates and/or controls storage and other information management operations performed by the information management system  100 , e.g., to protect and control the primary data  112  and secondary copies  116  of data and metadata. 
     As shown by the dashed, arrowed lines, the storage manager  140  may communicate with and/or control some or all elements of the information management system  100 , such as the data agents  142  and media agents  144 . Thus, in certain embodiments, control information originates from the storage manager  140 , whereas payload data and metadata is generally communicated between the data agents  142  and the media agents  144  (or otherwise between the client computing device(s)  102  and the secondary storage computing device(s)  106 ), e.g., at the direction of the storage manager  140 . In other embodiments, some information management operations are controlled by other components in the information management system  100  (e.g., the media agent(s)  144  or data agent(s)  142 ), instead of or in combination with the storage manager  140 . 
     According to certain embodiments, the storage manager provides one or more of the following functions:
         initiating execution of secondary copy operations;   managing secondary storage devices  108  and inventory/capacity of the same;   allocating secondary storage devices  108  for secondary storage operations;   monitoring completion of and providing status reporting related to secondary storage operations;   tracking age information relating to secondary copies  116 , secondary storage devices  108 , and comparing the age information against retention guidelines;   tracking movement of data within the information management system  100 ;   tracking logical associations between components in the information management system  100 ;   protecting metadata associated with the information management system  100 ; and   implementing operations management functionality.       

     The storage manager  140  may maintain a database  146  of management-related data and information management policies  148 . The database  146  may include a management index  150  or other data structure that stores logical associations between components of the system, user preferences and/or profiles (e.g., preferences regarding encryption, compression, or deduplication of primary or secondary copy data, preferences regarding the scheduling, type, or other aspects of primary or secondary copy or other operations, mappings of particular information management users or user accounts to certain computing devices or other components, etc.), management tasks, media containerization, or other useful data. For example, the storage manager  140  may use the index  150  to track logical associations between media agents  144  and secondary storage devices  108  and/or movement of data from primary storage devices  104  to secondary storage devices  108 . 
     Administrators and other employees may be able to manually configure and initiate certain information management operations on an individual basis. But while this may be acceptable for some recovery operations or other relatively less frequent tasks, it is often not workable for implementing on-going organization-wide data protection and management. 
     Thus, the information management system  100  may utilize information management policies  148  for specifying and executing information management operations (e.g., on an automated basis). Generally, an information management policy  148  can include a data structure or other information source that specifies a set of parameters (e.g., criteria and rules) associated with storage or other information management operations. 
     The storage manager database  146  may maintain the information management policies  148  and associated data, although the information management policies  148  can be stored in any appropriate location. For instance, a storage policy may be stored as metadata in a media agent database  152  or in a secondary storage device  108  (e.g., as an archive copy) for use in restore operations or other information management operations, depending on the embodiment. Information management policies  148  are described further below. 
     According to certain embodiments, the storage manager database  146  comprises a relational database (e.g., an SQL database) for tracking metadata, such as metadata associated with secondary copy operations (e.g., what client computing devices  102  and corresponding data were protected). This and other metadata may additionally be stored in other locations, such as at the secondary storage computing devices  106  or on the secondary storage devices  108 , allowing data recovery without the use of the storage manager  140 . 
     As shown, the storage manager  140  may include a jobs agent  156 , a user interface  158 , and a management agent  154 , all of which may be implemented as interconnected software modules or application programs. 
     The jobs agent  156  in some embodiments initiates, controls, and/or monitors the status of some or all storage or other information management operations previously performed, currently being performed, or scheduled to be performed by the information management system  100 . For instance, the jobs agent  156  may access information management policies  148  to determine when and how to initiate and control secondary copy and other information management operations, as will be discussed further. 
     The user interface  158  may include information processing and display software, such as a graphical user interface (“GUI”), an application program interface (“API”), or other interactive interface through which users and system processes can retrieve information about the status of information management operations (e.g., storage operations) or issue instructions to the information management system  100  and its constituent components. 
     The storage manager  140  may also track information that permits it to select, designate, or otherwise identify content indices, deduplication databases, or similar databases or resources or data sets within its information management cell (or another cell) to be searched in response to certain queries. Such queries may be entered by the user via interaction with the user interface  158 . 
     Via the user interface  158 , users may optionally issue instructions to the components in the information management system  100  regarding performance of storage and recovery operations. For example, a user may modify a schedule concerning the number of pending secondary copy operations. As another example, a user may employ the GUI to view the status of pending storage operations or to monitor the status of certain components in the information management system  100  (e.g., the amount of capacity left in a storage device). 
     In general, the management agent  154  allows multiple information management systems  100  to communicate with one another. For example, the information management system  100  in some cases may be one information management subsystem or “cell” of a network of multiple cells adjacent to one another or otherwise logically related in a WAN or LAN. With this arrangement, the cells may be connected to one another through respective management agents  154 . 
     For instance, the management agent  154  can provide the storage manager  140  with the ability to communicate with other components within the information management system  100  (and/or other cells within a larger information management system) via network protocols and application programming interfaces (“APIs”) including, e.g., HTTP, HTTPS, FTP, REST, virtualization software APIs, cloud service provider APIs, and hosted service provider APIs. Inter-cell communication and hierarchy is described in greater detail in U.S. Pat. No. 7,035,880, which is incorporated by reference herein. 
     Data Agents 
     As discussed, a variety of different types of applications  110  can reside on a given client computing device  102 , including operating systems, database applications, e-mail applications, and virtual machines, just to name a few. And, as part of the as part of the process of creating and restoring secondary copies  116 , the client computing devices  102  may be tasked with processing and preparing the primary data  112  from these various different applications  110 . Moreover, the nature of the processing/preparation can differ across clients and application types, e.g., due to inherent structural and formatting differences between applications  110 . 
     The one or more data agent(s)  142  are therefore advantageously configured in some embodiments to assist in the performance of information management operations based on the type of data that is being protected, at a client-specific and/or application-specific level. 
     The data agent  142  may be a software module or component that is generally responsible for managing, initiating, or otherwise assisting in the performance of information management operations. For instance, the data agent  142  may take part in performing data storage operations such as the copying, archiving, migrating, replicating of primary data  112  stored in the primary storage device(s)  104 . The data agent  142  may receive control information from the storage manager  140 , such as commands to transfer copies of data objects, metadata, and other payload data to the media agents  144 . 
     In some embodiments, a data agent  142  may be distributed between the client computing device  102  and storage manager  140  (and any other intermediate components) or may be deployed from a remote location or its functions approximated by a remote process that performs some or all of the functions of data agent  142 . In addition, a data agent  142  may perform some functions provided by a media agent  144 , e.g., encryption and deduplication. 
     As indicated, each data agent  142  may be specialized for a particular application  110 , and the system can employ multiple data agents  142 , each of which may backup, migrate, and recover data associated with a different application  110 . For instance, different individual data agents  142  may be designed to handle Microsoft Exchange data, Lotus Notes data, Microsoft Windows file system data, Microsoft Active Directory Objects data, SQL Server data, SharePoint data, Oracle database data, SAP database data, virtual machines and/or associated data, and other types of data. 
     A file system data agent, for example, may handle data files and/or other file system information. If a client computing device  102  has two or more types of data, one data agent  142  may be used for each data type to copy, archive, migrate, and restore the client computing device  102  data. For example, to backup, migrate, and restore all of the data on a Microsoft Exchange server, the client computing device  102  may use one Microsoft Exchange Mailbox data agent  142  to backup the Exchange mailboxes, one Microsoft Exchange Database data agent  142  to backup the Exchange databases, one Microsoft Exchange Public Folder data agent  142  to backup the Exchange Public Folders, and one Microsoft Windows File System data agent  142  to backup the file system of the client computing device  102 . In such embodiments, these data agents  142  may be treated as four separate data agents  142  even though they reside on the same client computing device  102 . 
     Other embodiments may employ one or more generic data agents  142  that can handle and process data from two or more different applications  110 , or that can handle and process multiple data types, instead of or in addition to using specialized data agents  142 . For example, one generic data agent  142  may be used to back up, migrate and restore Microsoft Exchange Mailbox data and Microsoft Exchange Database data while another generic data agent may handle Microsoft Exchange Public Folder data and Microsoft Windows File System data. 
     Each data agent  142  may be configured to access data and/or metadata stored in the primary storage device(s)  104  associated with the data agent  142  and process the data as appropriate. For example, during a secondary copy operation, the data agent  142  may arrange or assemble the data and metadata into one or more files having a certain format (e.g., a particular backup or archive format) before transferring the file(s) to a media agent  144  or other component. The file(s) may include a list of files or other metadata. Each data agent  142  can also assist in restoring data or metadata to primary storage devices  104  from a secondary copy  116 . For instance, the data agent  142  may operate in conjunction with the storage manager  140  and one or more of the media agents  144  to restore data from secondary storage device(s)  108 . 
     Media Agents 
     As indicated above with respect to  FIG. 1A , off-loading certain responsibilities from the client computing devices  102  to intermediary components such as the media agent(s)  144  can provide a number of benefits including improved client computing device  102  operation, faster secondary copy operation performance, and enhanced scalability. As one specific example which will be discussed below in further detail, the media agent  144  can act as a local cache of copied data and/or metadata that it has stored to the secondary storage device(s)  108 , providing improved restore capabilities. 
     Generally speaking, a media agent  144  may be implemented as a software module that manages, coordinates, and facilitates the transmission of data, as directed by the storage manager  140 , between a client computing device  102  and one or more secondary storage devices  108 . Whereas the storage manager  140  controls the operation of the information management system  100 , the media agent  144  generally provides a portal to secondary storage devices  108 . 
     Media agents  144  can comprise logically and/or physically separate nodes in the information management system  100  (e.g., separate from the client computing devices  102 , storage manager  140 , and/or secondary storage devices  108 ). In addition, each media agent  144  may reside on a dedicated secondary storage computing device  106  in some cases, while in other embodiments a plurality of media agents  144  reside on the same secondary storage computing device  106 . 
     A media agent  144  (and corresponding media agent database  152 ) may be considered to be “associated with” a particular secondary storage device  108  if that media agent  144  is capable of one or more of: routing and/or storing data to the particular secondary storage device  108 , coordinating the routing and/or storing of data to the particular secondary storage device  108 , retrieving data from the particular secondary storage device  108 , and coordinating the retrieval of data from a particular secondary storage device  108 . 
     While media agent(s)  144  are generally associated with one or more secondary storage devices  108 , the media agents  144  in certain embodiments are physically separate from the secondary storage devices  108 . For instance, the media agents  144  may reside on secondary storage computing devices  106  having different housings or packages than the secondary storage devices  108 . In one example, a media agent  144  resides on a first server computer and is in communication with a secondary storage device(s)  108  residing in a separate, rack-mounted RAID-based system. 
     In operation, a media agent  144  associated with a particular secondary storage device  108  may instruct the secondary storage device  108  (e.g., a tape library) to use a robotic arm or other retrieval means to load or eject a certain storage media, and to subsequently archive, migrate, or retrieve data to or from that media, e.g., for the purpose of restoring the data to a client computing device  102 . The media agent  144  may communicate with a secondary storage device  108  via a suitable communications link, such as a SCSI or Fiber Channel link. 
     As shown, each media agent  144  may maintain an associated media agent database  152 . The media agent database  152  may be stored in a disk or other storage device (not shown) that is local to the secondary storage computing device  106  on which the media agent  144  resides. In other cases, the media agent database  152  is stored remotely from the secondary storage computing device  106 . 
     The media agent database  152  can include, among other things, an index  153  including data generated during secondary copy operations and other storage or information management operations. The index  153  provides a media agent  144  or other component with a fast and efficient mechanism for locating secondary copies  116  or other data stored in the secondary storage devices  108 . In one configuration, a storage manager index  150  or other data structure may store data associating a client computing device  102  with a particular media agent  144  and/or secondary storage device  108 , as specified in a storage policy. A media agent index  153  or other data structure associated with the particular media agent  144  may in turn include information about the stored data. 
     For instance, for each secondary copy  116 , the index  153  may include metadata such as a list of the data objects (e.g., files/subdirectories, database objects, mailbox objects, etc.), a path to the secondary copy  116  on the corresponding secondary storage device  108 , location information indicating where the data objects are stored in the secondary storage device  108 , when the data objects were created or modified, etc. Thus, the index  153  includes metadata associated with the secondary copies  116  that is readily available for use in storage operations and other activities without having to be first retrieved from the secondary storage device  108 . In yet further embodiments, some or all of the data in the index  153  may instead or additionally be stored along with the data in a secondary storage device  108 , e.g., with a copy of the index  153 . 
     Because the index  153  maintained in the database  152  may operate as a cache, it can also be referred to as an index cache. In such cases, information stored in the index cache  153  typically comprises data that reflects certain particulars about storage operations that have occurred relatively recently. After some triggering event, such as after a certain period of time elapses, or the index cache  153  reaches a particular size, the index cache  153  may be copied or migrated to a secondary storage device(s)  108 . This information may need to be retrieved and uploaded back into the index cache  153  or otherwise restored to a media agent  144  to facilitate retrieval of data from the secondary storage device(s)  108 . In some embodiments, the cached information may include format or containerization information related to archives or other files stored on the storage device(s)  108 . In this manner, the index cache  153  allows for accelerated restores. 
     In some alternative embodiments the media agent  144  generally acts as a coordinator or facilitator of storage operations between client computing devices  102  and corresponding secondary storage devices  108 , but does not actually write the data to the secondary storage device  108 . For instance, the storage manager  140  (or the media agent  144 ) may instruct a client computing device  102  and secondary storage device  108  to communicate with one another directly. In such a case the client computing device  102  transmits the data directly to the secondary storage device  108  according to the received instructions, and vice versa. In some such cases, the media agent  144  may still receive, process, and/or maintain metadata related to the storage operations. Moreover, in these embodiments, the payload data can flow through the media agent  144  for the purposes of populating the index cache  153  maintained in the media agent database  152 , but not for writing to the secondary storage device  108 . 
     The media agent  144  and/or other components such as the storage manager  140  may in some cases incorporate additional functionality, such as data classification, content indexing, deduplication, encryption, compression, and the like. Further details regarding these and other functions are described below. 
     Distributed, Scalable Architecture 
     As described, certain functions of the information management system  100  can be distributed amongst various physical and/or logical components in the system. For instance, one or more of the storage manager  140 , data agents  142 , and media agents  144  may reside on computing devices that are physically separate from one another. This architecture can provide a number of benefits. 
     For instance, hardware and software design choices for each distributed component can be targeted to suit its particular function. The secondary computing devices  106  on which the media agents  144  reside can be tailored for interaction with associated secondary storage devices  108  and provide fast index cache operation, among other specific tasks. Similarly, the client computing device(s)  102  can be selected to effectively service the applications  110  residing thereon, in order to efficiently produce and store primary data  112 . 
     Moreover, in some cases, one or more of the individual components in the information management system  100  can be distributed to multiple, separate computing devices. As one example, for large file systems where the amount of data stored in the storage management database  146  is relatively large, the management database  146  may be migrated to or otherwise reside on a specialized database server (e.g., an SQL server) separate from a server that implements the other functions of the storage manager  140 . This configuration can provide added protection because the database  146  can be protected with standard database utilities (e.g., SQL log shipping or database replication) independent from other functions of the storage manager  140 . The database  146  can be efficiently replicated to a remote site for use in the event of a disaster or other data loss incident at the primary site. Or the database  146  can be replicated to another computing device within the same site, such as to a higher performance machine in the event that a storage manager host device can no longer service the needs of a growing information management system  100 . 
     The distributed architecture also provides both scalability and efficient component utilization.  FIG. 1D  shows an embodiment of the information management system  100  including a plurality of client computing devices  102  and associated data agents  142  as well as a plurality of secondary storage computing devices  106  and associated media agents  144 . 
     Additional components can be added or subtracted based on the evolving needs of the information management system  100 . For instance, depending on where bottlenecks are identified, administrators can add additional client computing devices  102 , secondary storage devices  106  (and corresponding media agents  144 ), and/or secondary storage devices  108 . 
     Moreover, each client computing device  102  in some embodiments can communicate with any of the media agents  144 , e.g., as directed by the storage manager  140 . And each media agent  144  may be able to communicate with any of the secondary storage devices  108 , e.g., as directed by the storage manager  140 . Thus, operations can be routed to the secondary storage devices  108  in a dynamic and highly flexible manner. Further examples of scalable systems capable of dynamic storage operations are provided in U.S. Pat. No. 7,246,207, which is incorporated by reference herein. 
     In alternative configurations, certain components are not distributed and may instead reside and execute on the same computing device. For example, in some embodiments one or more data agents  142  and the storage manager  140  reside on the same client computing device  102 . In another embodiment, one or more data agents  142  and one or more media agents  144  reside on a single computing device. 
     Exemplary Types of Information Management Operations 
     In order to protect and leverage stored data, the information management system  100  can be configured to perform a variety of information management operations. As will be described, these operations can generally include secondary copy and other data movement operations, processing and data manipulation operations, and management operations. 
     Data Movement Operations 
     Data movement operations according to certain embodiments are generally operations that involve the copying or migration of data (e.g., payload data) between different locations in the information management system  100 . For example, data movement operations can include operations in which stored data is copied, migrated, or otherwise transferred from primary storage device(s)  104  to secondary storage device(s)  108 , from secondary storage device(s)  108  to different secondary storage device(s)  108 , or from primary storage device(s)  104  to different primary storage device(s)  104 . 
     Data movement operations can include by way of example, backup operations, archive operations, information lifecycle management operations such as hierarchical storage management operations, replication operations (e.g., continuous data replication operations), snapshot operations, deduplication operations, single-instancing operations, auxiliary copy operations, and the like. As will be discussed, some of these operations involve the copying, migration or other movement of data, without actually creating multiple, distinct copies. Nonetheless, some or all of these operations are referred to as “copy” operations for simplicity. 
     Backup Operations 
     A backup operation creates a copy of primary data  112  at a particular point in time. Each subsequent backup copy may be maintained independently of the first. Further, a backup copy in some embodiments is stored in a backup format. This can be in contrast to the version in primary data  112  from which the backup copy is derived, and which may instead be stored in a native format of the source application(s)  110 . In various cases, backup copies can be stored in a format in which the data is compressed, encrypted, deduplicated, and/or otherwise modified from the original application format. For example, a backup copy may be stored in a backup format that facilitates compression and/or efficient long-term storage. 
     Backup copies can have relatively long retention periods as compared to primary data  112 , and may be stored on media with slower retrieval times than primary data  112  and certain other types of secondary copies  116 . On the other hand, backups may have relatively shorter retention periods than some other types of secondary copies  116 , such as archive copies (described below). Backups may sometimes be stored at on offsite location. 
     Backup operations can include full, synthetic or incremental backups. A full backup in some embodiments is generally a complete image of the data to be protected. However, because full backup copies can consume a relatively large amount of storage, it can be useful to use a full backup copy as a baseline and only store changes relative to the full backup copy for subsequent backup copies. 
     For instance, a differential backup operation (or cumulative incremental backup operation) tracks and stores changes that have occurred since the last full backup. Differential backups can grow quickly in size, but can provide relatively efficient restore times because a restore can be completed in some cases using only the full backup copy and the latest differential copy. 
     An incremental backup operation generally tracks and stores changes since the most recent backup copy of any type, which can greatly reduce storage utilization. In some cases, however, restore times can be relatively long in comparison to full or differential backups because completing a restore operation may involve accessing a full backup in addition to multiple incremental backups. 
     Any of the above types of backup operations can be at the file-level, e.g., where the information management system  100  generally tracks changes to files at the file-level, and includes copies of files in the backup copy. In other cases, block-level backups are employed, where files are broken into constituent blocks, and changes are tracked at the block-level. Upon restore, the information management system  100  reassembles the blocks into files in a transparent fashion. 
     Far less data may actually be transferred and copied to the secondary storage devices  108  during a block-level copy than during a file-level copy, resulting in faster execution times. However, when restoring a block-level copy, the process of locating constituent blocks can sometimes result in longer restore times as compared to file-level backups. Similar to backup operations, the other types of secondary copy operations described herein can also be implemented at either the file-level or the block-level. 
     Archive Operations 
     Because backup operations generally involve maintaining a version of the copied data in primary data  112  and also maintaining backup copies in secondary storage device(s)  108 , they can consume significant storage capacity. To help reduce storage consumption, an archive operation according to certain embodiments creates a secondary copy  116  by both copying and removing source data. Or, seen another way, archive operations can involve moving some or all of the source data to the archive destination. Thus, data satisfying criteria for removal (e.g., data of a threshold age or size) from the source copy may be removed from source storage. Archive copies are sometimes stored in an archive format or other non-native application format. The source data may be primary data  112  or a secondary copy  116 , depending on the situation. As with backup copies, archive copies can be stored in a format in which the data is compressed, encrypted, deduplicated, and/or otherwise modified from the original application format. 
     In addition, archive copies may be retained for relatively long periods of time (e.g., years) and, in some cases, are never deleted. Archive copies are generally retained for longer periods of time than backup copies, for example. In certain embodiments, archive copies may be made and kept for extended periods in order to meet compliance regulations. 
     Moreover, when primary data  112  is archived, in some cases the archived primary data  112  or a portion thereof is deleted when creating the archive copy. Thus, archiving can serve the purpose of freeing up space in the primary storage device(s)  104 . Similarly, when a secondary copy  116  is archived, the secondary copy  116  may be deleted, and an archive copy can therefore serve the purpose of freeing up space in secondary storage device(s)  108 . In contrast, source copies often remain intact when creating backup copies. 
     Snapshot Operations 
     Snapshot operations can provide a relatively lightweight, efficient mechanism for protecting data. From an end-user viewpoint, a snapshot may be thought of as an “instant” image of the primary data  112  at a given point in time. In one embodiment, a snapshot may generally capture the directory structure of an object in primary data  112  such as a file or volume or other data set at a particular moment in time and may also preserve file attributes and contents. A snapshot in some cases is created relatively quickly, e.g., substantially instantly, using a minimum amount of file space, but may still function as a conventional file system backup. 
     A snapshot copy in many cases can be made quickly and without significantly impacting primary computing resources because large amounts of data need not be copied or moved. In some embodiments, a snapshot may exist as a virtual file system, parallel to the actual file system. Users in some cases gain read-only access to the record of files and directories of the snapshot. By electing to restore primary data  112  from a snapshot taken at a given point in time, users may also return the current file system to the state of the file system that existed when the snapshot was taken. 
     Some types of snapshots do not actually create another physical copy of all the data as it existed at the particular point in time, but may simply create pointers that are able to map files and directories to specific memory locations (e.g., disk blocks) where the data resides, as it existed at the particular point in time. For example, a snapshot copy may include a set of pointers derived from the file system or an application. Each pointer points to a respective stored data block, so collectively, the set of pointers reflect the storage location and state of the data object (e.g., file(s) or volume(s) or data set(s)) at a particular point in time when the snapshot copy was created. 
     In some embodiments, once a snapshot has been taken, subsequent changes to the file system typically do not overwrite the blocks in use at the time of the snapshot. Therefore, the initial snapshot may use only a small amount of disk space needed to record a mapping or other data structure representing or otherwise tracking the blocks that correspond to the current state of the file system. Additional disk space is usually required only when files and directories are actually modified later. Furthermore, when files are modified, typically only the pointers which map to blocks are copied, not the blocks themselves. In some embodiments, for example in the case of “copy-on-write” snapshots, when a block changes in primary storage, the block is copied to secondary storage or cached in primary storage before the block is overwritten in primary storage. The snapshot mapping of file system data is also updated to reflect the changed block(s) at that particular point in time. In some other cases, a snapshot includes a full physical copy of all or substantially all of the data represented by the snapshot. Further examples of snapshot operations are provided in U.S. Pat. No. 7,529,782, which is incorporated by reference herein. 
     Replication Operations 
     Another type of secondary copy operation is a replication operation. Some types of secondary copies  116  are used to periodically capture images of primary data  112  at particular points in time (e.g., backups, archives, and snapshots). However, it can also be useful for recovery purposes to protect primary data  112  in a more continuous fashion, by replicating the primary data  112  substantially as changes occur. In some cases a replication copy can be a mirror copy, for instance, where changes made to primary data  112  are mirrored to another location (e.g., to secondary storage device(s)  108 ). By copying each write operation to the replication copy, two storage systems are kept synchronized or substantially synchronized so that they are virtually identical at approximately the same time. Where entire disk volumes are mirrored, however, mirroring can require significant amount of storage space and utilizes a large amount of processing resources. 
     According to some embodiments storage operations are performed on replicated data that represents a recoverable state, or “known good state” of a particular application running on the source system. For instance, in certain embodiments, known good replication copies may be viewed as copies of primary data  112 . This feature allows the system to directly access, copy, restore, backup or otherwise manipulate the replication copies as if the data was the “live”, primary data  112 . This can reduce access time, storage utilization, and impact on source applications  110 , among other benefits. 
     Based on known good state information, the information management system  100  can replicate sections of application data that represent a recoverable state rather than rote copying of blocks of data. Examples of compatible replication operations (e.g., continuous data replication) are provided in U.S. Pat. No. 7,617,262, which is incorporated by reference herein. 
     Deduplication/Single-Instancing Operations 
     Another type of data movement operation is deduplication, which is useful to reduce the amount of data within the system. For instance, some or all of the above-described secondary storage operations can involve deduplication in some fashion. New data is read, broken down into blocks (e.g., sub-file level blocks) of a selected granularity, compared with blocks that are already stored, and only the new blocks are stored. Blocks that already exist are represented as pointers to the already stored data. 
     In order to stream-line the comparison process, the information management system  100  may calculate and/or store signatures (e.g., hashes) corresponding to the individual data blocks and compare the hashes instead of comparing entire data blocks. In some cases, only a single instance of each element is stored, and deduplication operations may therefore be referred to interchangeably as “single-instancing” operations. Depending on the implementation, however, deduplication or single-instancing operations can store more than one instance of certain data blocks, but nonetheless significantly reduce data redundancy. Moreover, single-instancing in some cases is distinguished from deduplication as a process of analyzing and reducing data at the file level, rather than the sub-file level. 
     Depending on the embodiment, deduplication blocks can be of fixed or variable length. Using variable length blocks can provide enhanced deduplication by responding to changes in the data stream, but can involve complex processing. In some cases, the information management system  100  utilizes a technique for dynamically aligning deduplication blocks (e.g., fixed-length blocks) based on changing content in the data stream, as described in U.S. Pat. Pub. No. 2012/0084269, which is incorporated by reference herein. 
     The information management system  100  can perform deduplication in a variety of manners at a variety of locations in the information management system  100 . For instance, in some embodiments, the information management system  100  implements “target-side” deduplication by deduplicating data (e.g., secondary copies  116 ) stored in the secondary storage devices  108 . In some such cases, the media agents  144  are generally configured to manage the deduplication process. For instance, one or more of the media agents  144  maintain a corresponding deduplication database that stores deduplication information (e.g., datablock signatures). Examples of such a configuration are provided in U.S. Pat. Pub. No. 2012/0150826, which is incorporated by reference herein. Deduplication can also be performed on the “source-side” (or “client-side”), e.g., to reduce the amount of traffic between the media agents  144  and the client computing device(s)  102  and/or reduce redundant data stored in the primary storage devices  104 . Examples of such deduplication techniques are provided in U.S. Pat. Pub. No. 2012/0150818, which is incorporated by reference herein. 
     Information Lifecycle Management and Hierarchical Storage Management Operations 
     In some embodiments, files and other data over their lifetime move from more expensive, quick access storage to less expensive, slower access storage. Operations associated with moving data through various tiers of storage are sometimes referred to as information lifecycle management (ILM) operations. 
     One type of ILM operation is a hierarchical storage management (HSM) operation. A HSM operation is generally an operation for automatically moving data between classes of storage devices, such as between high-cost and low-cost storage devices. For instance, an HSM operation may involve movement of data from primary storage devices  104  to secondary storage devices  108 , or between tiers of secondary storage devices  108 . With each tier, the storage devices may be progressively relatively cheaper, have relatively slower access/restore times, etc. For example, movement of data between tiers may occur as data becomes less important over time. 
     In some embodiments, an HSM operation is similar to an archive operation in that creating an HSM copy may (though not always) involve deleting some of the source data. For example, an HSM copy may include data from primary data  112  or a secondary copy  116  that is larger than a given size threshold or older than a given age threshold and that is stored in a backup format. 
     Often, and unlike some types of archive copies, HSM data that is removed or aged from the source copy is replaced by a logical reference pointer or stub. The reference pointer or stub can be stored in the primary storage device  104  to replace the deleted data in primary data  112  (or other source copy) and to point to or otherwise indicate the new location in a secondary storage device  108 . 
     According to one example, files are generally moved between higher and lower cost storage depending on how often the files are accessed. When a user requests access to the HSM data that has been removed or migrated, the information management system  100  uses the stub to locate the data and often make recovery of the data appear transparent, even though the HSM data may be stored at a location different from the remaining source data. The stub may also include some metadata associated with the corresponding data, so that a file system and/or application can provide some information about the data object and/or a limited-functionality version (e.g., a preview) of the data object. 
     An HSM copy may be stored in a format other than the native application format (e.g., where the data is compressed, encrypted, deduplicated, and/or otherwise modified from the original application format). In some cases, copies which involve the removal of data from source storage and the maintenance of stub or other logical reference information on source storage may be referred to generally as “on-line archive copies”. On the other hand, copies which involve the removal of data from source storage without the maintenance of stub or other logical reference information on source storage may be referred to as “off-line archive copies”. 
     Auxiliary Copy and Disaster Recovery Operations 
     An auxiliary copy is generally a copy operation in which a copy is created of an existing secondary copy  116 . For instance, an initial or “primary” secondary copy  116  may be generated using or otherwise be derived from primary data  112 , whereas an auxiliary copy is generated from the initial secondary copy  116 . Auxiliary copies can be used to create additional standby copies of data and may reside on different secondary storage devices  108  than initial secondary copies  116 . Thus, auxiliary copies can be used for recovery purposes if initial secondary copies  116  become unavailable. Exemplary compatible auxiliary copy techniques are described in further detail in U.S. Pat. No. 8,230,195, which is incorporated by reference herein. 
     The information management system  100  may also perform disaster recovery operations that make or retain disaster recovery copies, often as secondary, high-availability disk copies. The information management system  100  may create secondary disk copies and store the copies at disaster recovery locations using auxiliary copy or replication operations, such as continuous data replication technologies. Depending on the particular data protection goals, disaster recovery locations can be remote from the client computing devices  102  and primary storage devices  104 , remote from some or all of the secondary storage devices  108 , or both. 
     Data Processing and Manipulation Operations 
     As indicated, the information management system  100  can also be configured to implement certain data manipulation operations, which according to certain embodiments are generally operations involving the processing or modification of stored data. Some data manipulation operations include content indexing operations and classification operations can be useful in leveraging the data under management to provide enhanced search and other features. Other data manipulation operations such as compression and encryption can provide data reduction and security benefits, respectively. 
     Data manipulation operations can be different than data movement operations in that they do not necessarily involve the copying, migration or other transfer of data (e.g., primary data  112  or secondary copies  116 ) between different locations in the system. For instance, data manipulation operations may involve processing (e.g., offline processing) or modification of already stored primary data  112  and/or secondary copies  116 . However, in some embodiments data manipulation operations are performed in conjunction with data movement operations. As one example, the information management system  100  may encrypt data while performing an archive operation. 
     Content Indexing 
     In some embodiments, the information management system  100  “content indexes” data stored within the primary data  112  and/or secondary copies  116 , providing enhanced search capabilities for data discovery and other purposes. The content indexing can be used to identify files or other data objects having pre-defined content (e.g., user-defined keywords or phrases), metadata (e.g., email metadata such as “to”, “from”, “cc”, “bcc”, attachment name, received time, etc.). 
     The information management system  100  generally organizes and catalogues the results in a content index, which may be stored within the media agent database  152 , for example. The content index can also include the storage locations of (or pointer references to) the indexed data in the primary data  112  or secondary copies  116 , as appropriate. The results may also be stored, in the form of a content index database or otherwise, elsewhere in the information management system  100  (e.g., in the primary storage devices  104 , or in the secondary storage device  108 ). Such index data provides the storage manager  140  or another component with an efficient mechanism for locating primary data  112  and/or secondary copies  116  of data objects that match particular criteria. 
     For instance, search criteria can be specified by a user through user interface  158  of the storage manager  140 . In some cases, the information management system  100  analyzes data and/or metadata in secondary copies  116  to create an “off-line” content index, without significantly impacting the performance of the client computing devices  102 . Depending on the embodiment, the system can also implement “on-line” content indexing, e.g., of primary data  112 . Examples of compatible content indexing techniques are provided in U.S. Pat. No. 8,170,995, which is incorporated by reference herein. 
     Classification Operations—Metabase 
     In order to help leverage the data stored in the information management system  100 , one or more components can be configured to scan data and/or associated metadata for classification purposes to populate a metabase of information. Such scanned, classified data and/or metadata may be included in a separate database and/or on a separate storage device from primary data  112  (and/or secondary copies  116 ), such that metabase related operations do not significantly impact performance on other components in the information management system  100 . 
     In other cases, the metabase(s) may be stored along with primary data  112  and/or secondary copies  116 . Files or other data objects can be associated with user-specified identifiers (e.g., tag entries) in the media agent  144  (or other indices) to facilitate searches of stored data objects. Among a number of other benefits, the metabase can also allow efficient, automatic identification of files or other data objects to associate with secondary copy or other information management operations (e.g., in lieu of scanning an entire file system). Examples of compatible metabases and data classification operations are provided in U.S. Pat. Nos. 8,229,954 and 7,747,579, which are incorporated by reference herein. 
     Encryption Operations 
     The information management system  100  in some cases is configured to process data (e.g., files or other data objects, secondary copies  116 , etc.), according to an appropriate encryption algorithm (e.g., Blowfish, Advanced Encryption Standard [AES], Triple Data Encryption Standard [3-DES], etc.) to limit access and provide data security in the information management system  100 . 
     The information management system  100  in some cases encrypts the data at the client level, such that the client computing devices  102  (e.g., the data agents  142 ) encrypt the data prior to forwarding the data to other components, e.g., before sending the data media agents  144  during a secondary copy operation. In such cases, the client computing device  102  may maintain or have access to an encryption key or passphrase for decrypting the data upon restore. Encryption can also occur when creating copies of secondary copies, e.g., when creating auxiliary copies. In yet further embodiments, the secondary storage devices  108  can implement built-in, high performance hardware encryption. 
     Management Operations 
     Certain embodiments leverage the integrated, ubiquitous nature of the information management system  100  to provide useful system-wide management functions. As two non-limiting examples, the information management system  100  can be configured to implement operations management and e-discovery functions. 
     Operations management can generally include monitoring and managing the health and performance of information management system  100  by, without limitation, performing error tracking, generating granular storage/performance metrics (e.g., job success/failure information, deduplication efficiency, etc.), generating storage modeling and costing information, and the like. 
     Such information can be provided to users via the user interface  158  in a single, integrated view. For instance, the integrated user interface  158  can include an option to show a “virtual view” of the system that graphically depicts the various components in the system using appropriate icons. The operations management functionality can facilitate planning and decision-making. For example, in some embodiments, a user may view the status of some or all jobs as well as the status of each component of the information management system  100 . Users may then plan and make decisions based on this data. For instance, a user may view high-level information regarding storage operations for the information management system  100 , such as job status, component status, resource status (e.g., network pathways, etc.), and other information. The user may also drill down or use other means to obtain more detailed information regarding a particular component, job, or the like. 
     In some cases the information management system  100  alerts a user such as a system administrator when a particular resource is unavailable or congested. For example, a particular primary storage device  104  or secondary storage device  108  might be full or require additional capacity. Or a component may be unavailable due to hardware failure, software problems, or other reasons. In response, the information management system  100  may suggest solutions to such problems when they occur (or provide a warning prior to occurrence). For example, the storage manager  140  may alert the user that a secondary storage device  108  is full or otherwise congested. The storage manager  140  may then suggest, based on job and data storage information contained in its database  146 , an alternate secondary storage device  108 . 
     Other types of corrective actions may include suggesting an alternate data path to a particular primary or secondary storage device  104 ,  108 , or dividing data to be stored among various available primary or secondary storage devices  104 ,  108  as a load balancing measure or to otherwise optimize storage or retrieval time. Such suggestions or corrective actions may be performed automatically, if desired. Further examples of some compatible operations management techniques and of interfaces providing an integrated view of an information management system are provided in U.S. Pat. No. 7,343,453, which is incorporated by reference herein. In some embodiments, the storage manager  140  implements the operations management functions described herein. 
     The information management system  100  can also be configured to perform system-wide e-discovery operations in some embodiments. In general, e-discovery operations provide a unified collection and search capability for data in the system, such as data stored in the secondary storage devices  108  (e.g., backups, archives, or other secondary copies  116 ). For example, the information management system  100  may construct and maintain a virtual repository for data stored in the information management system  100  that is integrated across source applications  110 , different storage device types, etc. According to some embodiments, e-discovery utilizes other techniques described herein, such as data classification and/or content indexing. 
     Information Management Policies 
     As indicated previously, an information management policy  148  can include a data structure or other information source that specifies a set of parameters (e.g., criteria and rules) associated with secondary copy or other information management operations. 
     One type of information management policy  148  is a storage policy. According to certain embodiments, a storage policy generally comprises a logical container that defines (or includes information sufficient to determine) one or more of the following items: (1) what data will be associated with the storage policy; (2) a destination to which the data will be stored; (3) datapath information specifying how the data will be communicated to the destination; (4) the type of storage operation to be performed; and (5) retention information specifying how long the data will be retained at the destination. 
     Data associated with a storage policy can be logically organized into groups, which can be referred to as “sub-clients”. A sub-client may represent static or dynamic associations of portions of a data volume. Sub-clients may represent mutually exclusive portions. Thus, in certain embodiments, a portion of data may be given a label and the association is stored as a static entity in an index, database or other storage location. 
     Sub-clients may also be used as an effective administrative scheme of organizing data according to data type, department within the enterprise, storage preferences, or the like. Depending on the configuration, sub-clients can correspond to files, folders, virtual machines, databases, etc. In one exemplary scenario, an administrator may find it preferable to separate e-mail data from financial data using two different sub-clients. 
     A storage policy can define where data is stored by specifying a target or destination storage device (or group of storage devices). For instance, where the secondary storage device  108  includes a group of disk libraries, the storage policy may specify a particular disk library for storing the sub-clients associated with the policy. As another example, where the secondary storage devices  108  include one or more tape libraries, the storage policy may specify a particular tape library for storing the sub-clients associated with the storage policy, and may also specify a drive pool and a tape pool defining a group of tape drives and a group of tapes, respectively, for use in storing the sub-client data. 
     Datapath information can also be included in the storage policy. For instance, the storage policy may specify network pathways and components to utilize when moving the data to the destination storage device(s). In some embodiments, the storage policy specifies one or more media agents  144  for conveying data (e.g., one or more sub-clients) associated with the storage policy between the source (e.g., one or more host client computing devices  102 ) and destination (e.g., a particular target secondary storage device  108 ). 
     A storage policy can also specify the type(s) of operations associated with the storage policy, such as a backup, archive, snapshot, auxiliary copy, or the like. Retention information can specify how long the data will be kept, depending on organizational needs (e.g., a number of days, months, years, etc.) 
     The information management policies  148  may also include one or more scheduling policies specifying when and how often to perform operations. Scheduling information may specify with what frequency (e.g., hourly, weekly, daily, event-based, etc.) or under what triggering conditions secondary copy or other information management operations will take place. Scheduling policies in some cases are associated with particular components, such as particular sub-clients, client computing device  102 , and the like. In one configuration, a separate scheduling policy is maintained for particular sub-clients on a client computing device  102 . The scheduling policy specifies that those sub-clients are to be moved to secondary storage devices  108  every hour according to storage policies associated with the respective sub-clients. 
     When adding a new client computing device  102 , administrators can manually configure information management policies  148  and/or other settings, e.g., via the user interface  158 . However, this can be an involved process resulting in delays, and it may be desirable to begin data protecting operations quickly. 
     Thus, in some embodiments, the information management system  100  automatically applies a default configuration to client computing device  102 . As one example, when a data agent(s)  142  is installed on a client computing devices  102 , the installation script may register the client computing device  102  with the storage manager  140 , which in turn applies the default configuration to the new client computing device  102 . In this manner, data protection operations can begin substantially immediately. The default configuration can include a default storage policy, for example, and can specify any appropriate information sufficient to begin data protection operations. This can include a type of data protection operation, scheduling information, a target secondary storage device  108 , data path information (e.g., a particular media agent  144 ), and the like. 
     Other types of information management policies  148  are possible. For instance, the information management policies  148  can also include one or more audit or security policies. An audit policy is a set of preferences, rules and/or criteria that protect sensitive data in the information management system  100 . For example, an audit policy may define “sensitive objects” as files or objects that contain particular keywords (e.g. “confidential,” or “privileged”) and/or are associated with particular keywords (e.g., in metadata) or particular flags (e.g., in metadata identifying a document or email as personal, confidential, etc.). 
     An audit policy may further specify rules for handling sensitive objects. As an example, an audit policy may require that a reviewer approve the transfer of any sensitive objects to a cloud storage site, and that if approval is denied for a particular sensitive object, the sensitive object should be transferred to a local storage device  104  instead. To facilitate this approval, the audit policy may further specify how a secondary storage computing device  106  or other system component should notify a reviewer that a sensitive object is slated for transfer. 
     In some implementations, the information management policies  148  may include one or more provisioning policies. A provisioning policy can include a set of preferences, priorities, rules, and/or criteria that specify how clients  102  (or groups thereof) may utilize system resources, such as available storage on cloud storage and/or network bandwidth. A provisioning policy specifies, for example, data quotas for particular client computing devices  102  (e.g. a number of gigabytes that can be stored monthly, quarterly or annually). The storage manager  140  or other components may enforce the provisioning policy. For instance, the media agents  144  may enforce the policy when transferring data to secondary storage devices  108 . If a client computing device  102  exceeds a quota, a budget for the client computing device  102  (or associated department) is adjusted accordingly or an alert may trigger. 
     While the above types of information management policies  148  have been described as separate policies, one or more of these can be generally combined into a single information management policy  148 . For instance, a storage policy may also include or otherwise be associated with one or more scheduling, audit, or provisioning policies. Moreover, while storage policies are typically associated with moving and storing data, other policies may be associated with other types of information management operations. The following is a non-exhaustive list of items the information management policies  148  may specify:
         schedules or other timing information, e.g., specifying when and/or how often to perform information management operations;   the type of secondary copy  116  and/or secondary copy format (e.g., snapshot, backup, archive, HSM, etc.);   a location or a class or quality of storage for storing secondary copies  116  (e.g., one or more particular secondary storage devices  108 );   preferences regarding whether and how to encrypt, compress, deduplicate, or otherwise modify or transform secondary copies  116 ;   which system components and/or network pathways (e.g., preferred media agents  144 ) should be used to perform secondary storage operations;   resource allocation between different computing devices or other system components used in performing information management operations (e.g., bandwidth allocation, available storage capacity, etc.);   whether and how to synchronize or otherwise distribute files or other data objects across multiple computing devices or hosted services; and   retention information specifying the length of time primary data  112  and/or secondary copies  116  should be retained, e.g., in a particular class or tier of storage devices, or within the information management system  100 .       

     Policies can additionally specify or depend on a variety of historical or current criteria that may be used to determine which rules to apply to a particular data object, system component, or information management operation, such as:
         frequency with which primary data  112  or a secondary copy  116  of a data object or metadata has been or is predicted to be used, accessed, or modified;   time-related factors (e.g., aging information such as time since the creation or modification of a data object);   deduplication information (e.g., hashes, data blocks, deduplication block size, deduplication efficiency or other metrics);   an estimated or historic usage or cost associated with different components (e.g., with secondary storage devices  108 );   the identity of users, applications  110 , client computing devices  102  and/or other computing devices that created, accessed, modified, or otherwise utilized primary data  112  or secondary copies  116 ;   a relative sensitivity (e.g., confidentiality) of a data object, e.g., as determined by its content and/or metadata;   the current or historical storage capacity of various storage devices;   the current or historical network capacity of network pathways connecting various components within the storage operation cell;   access control lists or other security information; and   the content of a particular data object (e.g., its textual content) or of metadata associated with the data object.
 
Exemplary Storage Policy and Secondary Storage Operations
       

       FIG. 1E  shows a data flow data diagram depicting performance of storage operations by an embodiment of an information management system  100 , according to an exemplary data storage policy  148 A. The information management system  100  includes a storage manger  140 , a client computing device  102  having a file system data agent  142 A and an email data agent  142 B residing thereon, a primary storage device  104 , two media agents  144 A,  144 B, and two secondary storage devices  108 A,  108 B: a disk library  108 A and a tape library  108 B. As shown, the primary storage device  104  includes primary data  112 A,  112 B associated with a file system sub-client and an email sub-client, respectively. 
     As indicated by the dashed box, the second media agent  144 B and the tape library  108 B are “off-site”, and may therefore be remotely located from the other components in the information management system  100  (e.g., in a different city, office building, etc.). In this manner, information stored on the tape library  108 B may provide protection in the event of a disaster or other failure. 
     The file system sub-client and its associated primary data  112 A in certain embodiments generally comprise information generated by the file system and/or operating system of the client computing device  102 , and can include, for example, file system data (e.g., regular files, file tables, mount points, etc.), operating system data (e.g., registries, event logs, etc.), and the like. The e-mail sub-client, on the other hand, and its associated primary data  112 B, include data generated by an e-mail client application operating on the client computing device  102 , and can include mailbox information, folder information, emails, attachments, associated database information, and the like. As described above, the sub-clients can be logical containers, and the data included in the corresponding primary data  112 A,  112 B may or may not be stored contiguously. 
     The exemplary storage policy  148 A includes a backup copy rule set  160 , a disaster recovery copy rule set  162 , and a compliance copy rule set  164 . The backup copy rule set  160  specifies that it is associated with a file system sub-client  166  and an email sub-client  168 . Each of these sub-clients  166 ,  168  are associated with the particular client computing device  102 . The backup copy rule set  160  further specifies that the backup operation will be written to the disk library  108 A, and designates a particular media agent  144 A to convey the data to the disk library  108 A. Finally, the backup copy rule set  160  specifies that backup copies created according to the rule set  160  are scheduled to be generated on an hourly basis and to be retained for 30 days. In some other embodiments, scheduling information is not included in the storage policy  148 A, and is instead specified by a separate scheduling policy. 
     The disaster recovery copy rule set  162  is associated with the same two sub-clients  166 ,  168 . However, the disaster recovery copy rule set  162  is associated with the tape library  108 B, unlike the backup copy rule set  160 . Moreover, the disaster recovery copy rule set  162  specifies that a different media agent  144 B than the media agent  144 A associated with the backup copy rule set  160  will be used to convey the data to the tape library  108 B. As indicated, disaster recovery copies created according to the rule set  162  will be retained for 60 days, and will be generated on a daily basis. Disaster recovery copies generated according to the disaster recovery copy rule set  162  can provide protection in the event of a disaster or other data-loss event that would affect the backup copy  116 A maintained on the disk library  108 A. 
     The compliance copy rule set  164  is only associated with the email sub-client  166 , and not the file system sub-client  168 . Compliance copies generated according to the compliance copy rule set  164  will therefore not include primary data  112 A from the file system sub-client  166 . For instance, the organization may be under an obligation to store maintain copies of email data for a particular period of time (e.g., 10 years) to comply with state or federal regulations, while similar regulations do not apply to the file system data. The compliance copy rule set  164  is associated with the same tape library  108 B and media agent  144 B as the disaster recovery copy rule set  162 , although a different storage device or media agent could be used in other embodiments. Finally, the compliance copy rule set  164  specifies that copies generated under the compliance copy rule set  164  will be retained for 10 years, and will be generated on a quarterly basis. 
     At step  1 , the storage manager  140  initiates a backup operation according to the backup copy rule set  160 . For instance, a scheduling service running on the storage manager  140  accesses scheduling information from the backup copy rule set  160  or a separate scheduling policy associated with the client computing device  102 , and initiates a backup copy operation on an hourly basis. Thus, at the scheduled time slot the storage manager  140  sends instructions to the client computing device  102  to begin the backup operation. 
     At step  2 , the file system data agent  142 A and the email data agent  142 B residing on the client computing device  102  respond to the instructions received from the storage manager  140  by accessing and processing the primary data  112 A,  112 B involved in the copy operation from the primary storage device  104 . Because the operation is a backup copy operation, the data agent(s)  142 A,  142 B may format the data into a backup format or otherwise process the data. 
     At step  3 , the client computing device  102  communicates the retrieved, processed data to the first media agent  144 A, as directed by the storage manager  140 , according to the backup copy rule set  160 . In some other embodiments, the information management system  100  may implement a load-balancing, availability-based, or other appropriate algorithm to select from the available set of media agents  144 A,  144 B. Regardless of the manner the media agent  144 A is selected, the storage manager  140  may further keep a record in the storage manager database  140  of the association between the selected media agent  144 A and the client computing device  102  and/or between the selected media agent  144 A and the backup copy  116 A. 
     The target media agent  144 A receives the data from the client computing device  102 , and at step  4  conveys the data to the disk library  108 A to create the backup copy  116 A, again at the direction of the storage manager  140  and according to the backup copy rule set  160 . The secondary storage device  108 A can be selected in other ways. For instance, the media agent  144 A may have a dedicated association with a particular secondary storage device(s), or the storage manager  140  or media agent  144 A may select from a plurality of secondary storage devices, e.g., according to availability, using one of the techniques described in U.S. Pat. No. 7,246,207, which is incorporated by reference herein. 
     The media agent  144 A can also update its index  153  to include data and/or metadata related to the backup copy  116 A, such as information indicating where the backup copy  116 A resides on the disk library  108 A, data and metadata for cache retrieval, etc. After the 30 day retention period expires, the storage manager  140  instructs the media agent  144 A to delete the backup copy  116 A from the disk library  108 A. 
     At step  5 , the storage manager  140  initiates the creation of a disaster recovery copy  116 B according to the disaster recovery copy rule set  162 . For instance, at step  6 , based on instructions received from the storage manager  140  at step  5 , the specified media agent  144 B retrieves the most recent backup copy  116 A from the disk library  108 A. 
     At step  7 , again at the direction of the storage manager  140  and as specified in the disaster recovery copy rule set  162 , the media agent  144 B uses the retrieved data to create a disaster recovery copy  116 B on the tape library  108 B. In some cases, the disaster recovery copy  116 B is a direct, mirror copy of the backup copy  116 A, and remains in the backup format. In other embodiments, the disaster recovery copy  116 C may be generated in some other manner, such as by using the primary data  112 A,  112 B from the storage device  104  as source data. The disaster recovery copy operation is initiated once a day and the disaster recovery copies  116 A are deleted after 60 days. 
     At step  8 , the storage manager  140  initiates the creation of a compliance copy  116 C, according to the compliance copy rule set  164 . For instance, the storage manager  140  instructs the media agent  144 B to create the compliance copy  116 C on the tape library  108 B at step  9 , as specified in the compliance copy rule set  164 . In the example, the compliance copy  116 C is generated using the disaster recovery copy  116 B. In other embodiments, the compliance copy  116 C is instead generated using either the primary data  112 B corresponding to the email sub-client or using the backup copy  116 A from the disk library  108 A as source data. As specified, compliance copies  116 C are created quarterly, and are deleted after ten years. 
     While not shown in  FIG. 1E , at some later point in time, a restore operation can be initiated involving one or more of the secondary copies  116 A,  116 B,  116 C. As one example, a user may manually initiate a restore of the backup copy  116 A by interacting with the user interface  158  of the storage manager  140 . The storage manager  140  then accesses data in its index  150  (and/or the respective storage policy  148 A) associated with the selected backup copy  116 A to identify the appropriate media agent  144 A and/or secondary storage device  116 A. 
     In other cases, a media agent may be selected for use in the restore operation based on a load balancing algorithm, an availability based algorithm, or other criteria. The selected media agent  144 A retrieves the data from the disk library  108 A. For instance, the media agent  144 A may access its index  153  to identify a location of the backup copy  116 A on the disk library  108 A, or may access location information residing on the disk  108 A itself. 
     When the backup copy  116 A was recently created or accessed, the media agent  144 A accesses a cached version of the backup copy  116 A residing in the media agent index  153 , without having to access the disk library  108 A for some or all of the data. Once it has retrieved the backup copy  116 A, the media agent  144 A communicates the data to the source client computing device  102 . Upon receipt, the file system data agent  142 A and the email data agent  142 B may unpackage (e.g., restore from a backup format to the native application format) the data in the backup copy  116 A and restore the unpackaged data to the primary storage device  104 . 
     Exemplary Secondary Copy Formatting 
     The formatting and structure of secondary copies  116  can vary, depending on the embodiment. In some cases, secondary copies  116  are formatted as a series of logical data units or “chunks” (e.g., 512 MB, 1 GB, 2 GB, 4 GB, or 8 GB chunks). This can facilitate efficient communication and writing to secondary storage devices  108 , e.g., according to resource availability. For example, a single secondary copy  116  may be written on a chunk-by-chunk basis to a single secondary storage device  108  or across multiple secondary storage devices  108 . In some cases, users can select different chunk sizes, e.g., to improve throughput to tape storage devices. 
     Generally, each chunk can include a header and a payload. The payload can include files (or other data units) or subsets thereof included in the chunk, whereas the chunk header generally includes metadata relating to the chunk, some or all of which may be derived from the payload. For example, during a secondary copy operation, the media agent  144 , storage manager  140 , or other component may divide the associated files into chunks and generate headers for each chunk by processing the constituent files. 
     The headers can include a variety of information such as file identifier(s), volume(s), offset(s), or other information associated with the payload data items, a chunk sequence number, etc. Importantly, in addition to being stored with the secondary copy  116  on the secondary storage device  108 , the chunk headers can also be stored to the index  153  of the associated media agent(s)  144  and/or the storage manager index  150 . This is useful in some cases for providing faster processing of secondary copies  116  during restores or other operations. In some cases, once a chunk is successfully transferred to a secondary storage device  108 , the secondary storage device  108  returns an indication of receipt, e.g., to the media agent  144  and/or storage manager  140 , which may update their respective indexes  150 ,  153  accordingly. 
     During restore, chunks may be processed (e.g., by the media agent  144 ) according to the information in the chunk header to reassemble the files. Additional information relating to chunks can be found in U.S. Pat. No. 8,156,086, which is incorporated by reference herein. 
     Example Virtualized Systems Including Proxies for Performing Storage Operations 
       FIGS. 2A-2C  are block diagrams illustrative of embodiments of respective storage systems  200 ,  218 ,  228 , each including a proxy computing device  204  (also referred to as proxy client  204 ) communicating with at least one storage device  208  on behalf of at least one client computing device  206 ,  220 ,  230 . 
       FIG. 2A  is a block diagram illustrative of an embodiment of a storage system  200 . The system  200  includes a storage manager  202 , a proxy client computing device  204 , at least one virtual client computing device  206  (also referred to as virtual client  206 ), and a storage device  208 . The proxy client  204  communicates with the storage device  208  on behalf of virtual client(s)  206 . The components of the storage system  200  communicate with each other via any appropriate type of network, including wired or wireless networks including, but not limited to a SAN, LAN, WAN, the internet, etc. In some embodiments, the system can further include a proxy client storage device  205 . In certain embodiments, the proxy client storage device  205  is local to the proxy client  204 , while the storage device  208  is remotely located. Furthermore, the proxy client storage device  205  can store data that is not stored in the storage device  208  and that is accessible by the proxy client  204  and/or virtual clients  206 . For example, the proxy client storage device  205  can store executable files, system files, application files, and other files that are selected to not be stored in the storage device  208 . Accordingly, during backup operations in certain embodiments, the data stored in the proxy client storage device  205  is not backed up to the storage device  208 . In some embodiments, a subset of the files stored in the proxy client storage device  205  are backed up or otherwise copied to the storage device  208 . 
     The storage manager  202  can generally be configured to coordinate storage operations, and invokes the other modules to implement storage operations, e.g., according to a storage policy. The storage manager  202  can be similar to or the same as the storage manager  140  of  FIGS. 1A-1E . Similarly, the proxy client  204  and virtual client(s)  206  may be similar to or the same as the client computing device  102  described previously with respect to  FIGS. 1A-1E . For example, the proxy client  204  and virtual clients  206  can include one or more data agents  210 ,  212 , respectively. In the illustrative embodiment of  FIG. 2A , the proxy client  204  is a host computing device, and includes one or more of the virtual clients  206  instantiated thereon. For instance, the proxy client  204  may have a virtual machine manager (VMM) (not shown) instantiated thereon, which may also be referred to as a hypervisor. The VMM can implement a hardware virtualization allowing the virtual clients  206  to run concurrently on the host computer. The proxy client  204  may also be referred to herein interchangeably as one or more of a proxy device, proxy computing device, host, or host computing device. 
     The VMM, in certain embodiments, generally operates as a supervisory program, presenting the virtual clients  206  a virtual operating platform and managing execution of the virtual clients  206 . For instance, the virtual clients  206  may comprise guest operating systems running concurrently on the proxy client  204 . The operating systems associated with the virtual clients  206  can be the same type of operating system as the operating system that is running on the proxy client  204 . Or, in other configurations, the operating system associated with one or more of the proxy clients  206  may be of a different type than the operating system running on the proxy client  204 . Moreover, while each of the virtual clients  206  may have the same type of associated operating system in some cases, in other embodiments, one or more of the virtual clients  206  has a different associated operating system than one or more of the other virtual clients  206 . The specific types of operating systems executing on the proxy client  204  and the virtual clients  206  can vary. For instance, depending on the configuration, one or more of the following, or other operating systems can be used: Microsoft Windows, Unix, Linux, Mac OS X, Android, iOS and z/OS. 
     In some embodiments, such as where the proxy client  204  and the virtual clients  206  run the same type of operating system, the virtual clients  206  comprise operating system-level virtualizations. In such cases, each of the virtual clients  206  forms an isolated user-space instance. For instance, each of the virtual clients  206  can act as an isolated virtual server (e.g., a zone, such as a Solaris Zone) within the single operating system that is running on the proxy client  204 . In one such embodiment, the virtual clients each implement containers (e.g., Solaris Containers), where each container forms a combination of system resource controls and boundary separation, provided by zones, for example. 
     Each of the virtual clients  206  can further include one or more data agents  212 . In some embodiments the virtual clients  206  do not have direct access to the storage device  208 . Thus, as will described in greater detail, the virtual clients  206  communicate with the storage device  208  indirectly via the proxy client  204 . 
     The storage device  208  can include one or more storage devices of any appropriate type (e.g., hard-drive, tape, solid state, etc.) and can be a local storage device of the proxy client  204  or remote from the proxy client  204 , depending on the embodiment. 
     In some embodiments, the storage device  208  is capable of performing snapshot operations. And in some cases, the storage device  208  performs the snapshot operations substantially independently, using hardware, firmware and/or software residing on the storage device  208 . For instance, the storage device  208  may be capable of performing snapshot operations upon request, without intervention or oversight from any of the other components in the system  200 . Where the storage device  208  performs the snapshot operation in this self-contained fashion, without the involvement of the proxy client  204  or other components in the system  200 , the snapshot may be referred to as a “hardware snapshot”. In some embodiments, the system  200  is capable of performing “software snapshots” in which the proxy client  204  or other components in the system manage the snapshot operation. The storage device  208  is also capable of performing additional operations, such as, but not limited to, logical unit number (LUN) provisioning, snapshot queries, mapping LUNs to a host, and running storage reports for clients. 
     The proxy client  204  can be in communication with the storage device  208  over a network (e.g., a LAN or WAN). Furthermore, the storage device  208  can include sufficient storage capacity to serve the needs of not only the proxy client  204 , but also the hosted virtual clients  206 . The memory space of the storage  208  can be allocated amongst the various clients such that separate portions are dedicated to each virtual client  206  and to the proxy client  204 . Furthermore, the storage device  208  can store primary and/or secondary copies of data associated with the proxy client  204  and virtual client  206 . In some embodiments, the storage device  208  is similar to the primary storage device  104  of  FIGS. 1A-1E . In certain embodiments the storage device is similar to the secondary storage device  108  of  FIG. 1 . In yet further embodiments, the storage device  208  is similar to primary storage device  104  and/or secondary storage device  108  of  FIGS. 1A-1E . 
     Because the virtual clients  206  do not have direct access to the storage device  208 , the proxy client  204  is used to interface with the storage device  208  to perform certain storage operations on behalf of the virtual clients  206 . The storage operations can include, but are not limited to, the creation of a snapshot, the mounting and un-mounting of a snapshot, and reversion to a particular snapshot. For example, if a storage policy dictates that a snapshot is to be taken of data associated with the one of the virtual clients  206  (e.g., of the entire file system, or of select directories, folders or files associated with the virtual client  206 ), the storage manager  202  instructs the appropriate data agent(s)  212  on the virtual client  206  to perform the snapshot operation. In one embodiment, the storage manager  140  instructs the Microsoft Exchange data agent  212  to perform a snapshot of certain Microsoft Exchange production data of the virtual client  206 . The data agent  212  forwards the snapshot request to an appropriate data agent  210  or other component of the proxy client  204 . In turn, the proxy client  204  forwards the request to create the snapshot to the storage device  208  on behalf of the virtual client  206 . 
     In response to the request, the storage device  208  creates a snapshot of the desired virtual client data. The snapshot may reside in a portion of the storage device  208  dedicated to storing data for the particular virtual client  206 , for example. Or the storage device  208  may instead allocate space for snapshot requests in some other manner, e.g., based on an allocation policy maintained by the storage device  208 . 
     Similarly, when the virtual client  206  desires to mount a previously unmounted or unknown snapshot, the virtual client  206  can request the mounting of the data from the data agent  210  of the proxy client  204 . In turn, the proxy client  204  requests the mounting data, or disk array data from the storage device  208 . Upon retrieving the disk array information of the snapshot, the storage device  208  transmits the data to the proxy client  204 . The proxy client transmits the data to the virtual client  206  and the virtual client is then able to mount and/or access the snapshot as desired. 
       FIG. 2B  is a block diagram illustrative of an embodiment of a storage network environment  218  including a proxy client communicating with a storage device  208  on behalf of a client computing device  220  (also referred to as client  220 ). The storage manager  202 , proxy client  204  and storage device  208  can be similar to or the same as the corresponding components described previously with respect to  FIG. 2A . However, the client  220  of  FIG. 2B  is different from the virtual client  206  of  FIG. 2A . For example, the client  220  can be a distinct, non-virtual, physical device, separate from the proxy client  204 , such as a personal computer, workstation, server, etc. Although not illustrated in  FIG. 2B , the clients  220  can include their own storage devices similar to the proxy client storage device  205 , described in greater detail above with reference to  FIG. 2A . In addition, the client  220  can in some cases have direct access to the storage device  208  for performing certain functions. However, in some embodiments, the client  220  uses the proxy client  204  to perform one or more other functions, including storage operations (e.g., snapshots), for example. In some embodiments, the client  220  does not have direct access to the storage device  208 , and only communicates with the storage device  208  via the proxy client  204 . For example, in some instances it is desirable to give only a single client direct access to the storage device  208 , e.g., for performing certain storage operations (e.g., snapshots), such as where a security policy dictates such an arrangement. In this way, the security of the storage device can be maintained, and the likelihood of errors or problems occurring during storage operations can be decreased. 
     Storage operations can include, but are not limited to, creating a snapshot of the client  220 , mounting the snapshot information to the client  220 , and/or reverting to a previous snapshot of the client  220 . In some embodiments, the storage manager  202  can transmit a snapshot creation command to the client  220 . Using the data agent  222 , the client can request that the proxy client  204  perform the snapshot creation. The client  220  can make the request from the proxy client  204  via the data agent  210  of the proxy client  204 . Upon receiving the snapshot creation request, the proxy client  204  can request that the snapshot be created in the storage device  208 , as described in greater detail below with reference to  FIGS. 3A and 5 . Similarly, the client  220  can request the proxy client  204  to retrieve snapshot location information and/or other disk data, and request a reversion of a previous snapshot. 
       FIG. 2C  is a block diagram illustrative of an embodiment of a storage network environment  228  including a proxy client  204  communicating with a storage device  208  on behalf of a virtual client computing device  230  (also referred to as virtual client  230 ). The storage manager  202 , proxy client  204  and storage device  208  can be similar to or the same as the corresponding components described previously with respect to  FIGS. 2A and 2B . Furthermore, although not illustrated in  FIG. 2B , the proxy client  204  and virtual clients  230  can include their own storage devices similar to the proxy client storage device  205 , described in greater detail above with reference to  FIG. 2A . The virtual client  230  can be similar to or the same as the corresponding components can be similar to or the same as the virtual client  206  of  FIG. 2A , however, the virtual client  230  is not instantiated in the proxy client  204 , as is the virtual client  206  of  FIG. 2A . 
     Furthermore, unlike the configurations of  FIGS. 2A and 2B , the embodiment of  FIG. 2C  additionally includes a server  234  that is in direct communication with the storage device  208  and is also in direct communication with the proxy client  204  and the virtual client  230 . However, in some embodiments, the virtual clients  230  are not provided with direct access to the storage device  208 . For instance, as indicated by the dashed line, the virtual client  230  may communicate with the storage device  208  indirectly via the server  234 . In such a situation, the server  234  generally acts as a proxy for the virtual client  230  in relation to interaction with the storage device  208 . Or, the virtual client  230  may instead request that a storage operation be performed in the storage device by communicating the request to the proxy client  204 . In some embodiments, the data agent  232  of virtual client  230  communicates with the data agent  210  of the proxy client  204  to communicate the storage operation request. In turn, the proxy client  204  relays the request to the server  234 , which forwards the request on to the storage device  208 . 
     The storage device  208  receives the request and performs the desired storage operation. Upon completion of the storage operation, the storage device  208  transmits relevant information indicating that the storage operation has been completed to the server  234 , which forwards the information to the proxy client  204  (or directly to the virtual client  230 , depending on the embodiment). The proxy client  204  thereafter transmits the relevant data to the virtual client  230 . As described in greater detail above, once the virtual client  230  receives confirmation of the completion of the storage operation, the virtual client  230  can notify the storage manager  202  that the storage operation has been completed, and/or perform one or more additional steps using the relevant data received. For example, the virtual client  230  can use snapshot disk data (e.g., location information) to mount a snapshot to the virtual client  230 . 
       FIGS. 3A and 3B  are state diagrams illustrative of example interaction between the various components of the storage network environment  200  of  FIG. 2A . For purposes of simplicity, the proxy client storage device  205 , described in greater detail above with reference to  FIG. 2A , is not shown. Although  FIGS. 3A and 3B  are directed towards the storage network environment  200  illustrated in  FIG. 2A , certain aspects of the state diagrams are compatible with the environments shown in  FIGS. 2B and 2C . For instance, similar state diagrams may be illustrative of the interaction between the various components of the storage network environments of  FIGS. 2B and 2C . Thus, the state diagrams illustrated in  FIGS. 3A and 3B  should not be construed as limiting. 
       FIG. 3A  is a state diagram illustrative of the interaction between the various components of the storage network environment  200  to perform a storage operation (e.g., a snapshot). As illustrated, the storage manager  202  (1) transmits a storage operation command to the data agent  212  of the virtual client  206 . As mentioned previously, the storage operation command can include any number of different storage operations, such as a snapshot creation, a mounting of a snapshot to the virtual client, a reversion to a previous snapshot, and the like. Upon receiving the storage operation command, the virtual client  206  determines that it is unable to initiate the storage operation by itself directly sending the storage operation request to the storage device  208 , and (2) transmits a storage operation request to the data agent  210  of the proxy client  204 . Although illustrated as the data agent  212  communicating via the data agent  210 , the virtual client  206  can communicate with the proxy client  204  in any appropriate manner. 
     The storage operation request can include the information to perform the storage operation, and/or for the proxy client  204  to properly initiate the request to the storage device  208  on behalf of the virtual client  206 . For example, the storage operation request can include information regarding the particular portion within the storage device  208  that contains the virtual client  206  data, such as one or more address locations or ranges of address locations within the storage device  208 . In certain embodiments, the proxy client  204  uses the information from the storage operation request to determine the portion within the storage device  208  that is associated with the data of the virtual client  206 . For example, the proxy client  204  can use identifying information relating to the virtual client  206  (e.g., client ID) to determine those portions of the storage  208  that contain data associated with the virtual client  206 . The proxy client  204  (3) transmits the storage operation request to the storage device  208 . 
     Upon receiving the storage operation request, the storage device  208  (4) performs the requested storage operation. Upon completion of the storage operation, the storage device  208  (5) notifies the proxy client  204  that the storage operation has been completed. The proxy client  204  (6) transmits relevant data to the data agent  212  of the virtual client  206 . In some embodiments, the proxy client  204  transmits the relevant data using the data agent  210 . The relevant data can include any and all information to be used by the virtual client  206  to perform one or more operations, and to notify the storage manager  202 . In some embodiments, the relevant data can include data requested by the data agent  212  and/or data not requested by the data agent  212 . Upon receiving the data from the proxy client  204 , the virtual client  206  (7) notifies the storage manager  202  that the storage operation has been completed. 
       FIG. 3A  further illustrates an embodiment of the portion of the storage device  208  associated with the virtual client  206  that includes the virtual client&#39;s data and snapshots of the virtual client&#39; data. The portion of the storage device containing the virtual client&#39;s data can be an addressable space of the storage device and can include contiguous or non-contiguous addresses. In the illustrated embodiment, the portion of the storage device  208  that is associated with the virtual client  206  is labeled virtual client storage  310 . The virtual client storage  310  may store an initial copy of the virtual client&#39;s data, backup copies, and/or snapshots. In some embodiments, snapshots of the virtual client&#39;s data, or virtual client snapshots  312 , can reside in the same or different portion of the storage device  208  as the virtual client storage  310 . 
     Upon receiving a snapshot creation request, the storage device  208  performs a snapshot  312  of the virtual client storage  310  contained within the storage device  208 . The storage device  208  creates the virtual client snapshot  312  based on the snapshot request and/or on the data stored in the virtual client storage  310 . For instance, the snapshot  312  may comprise a set of pointers to the first portion  310  for un-modified virtual client data, as well as actual data copies for modified virtual client data, according to a copy-on-write scheme, for example. Upon completion of the snapshot creation, the storage device  208  notifies the proxy client  206  that the snapshot has been created. 
     The proxy client  204  transmits a snapshot identifier to the virtual client  206 . The virtual client  206  can use the snapshot identifier to access the snapshot or at least to verify that the snapshot has been created. For example, the virtual client  206  can include the snapshot identifier of a particular snapshot as part of a request (e.g., access requests, reversion requests, etc.) made to the proxy client  204 . The snapshot identifier can contain location information regarding the portion of memory within the storage device  208  that contains the particular snapshot and/or the proxy client  204  can include a look-up table to determine the portion of memory within the storage device  208  that includes the particular snapshot. Once the virtual client receives the snapshot identifier, or other relevant data, the virtual client  206  can notify the storage manager  202  that the snapshot has been created. 
       FIG. 3B  is a state diagram illustrative of the interaction between the various components of the storage network environment when the storage manager  202  issues a snapshot mount command. As illustrated in  FIG. 3B , the storage manager  202  (1) transmits a snapshot mount command to the virtual client  206 . The snapshot mount command can provide sufficient information such that the virtual client  206  can request that a snapshot be mounted to the virtual client  206 . For example, the snapshot mount command can include the snapshot identifier of the snapshot to be mounted, etc. In some embodiments, the snapshot mount command can be included as part of a request to access or read a snapshot previously created for the virtual client  206 . Upon receiving the snapshot mount command, and determining that the virtual client  206  does not already have access to the snapshot, the virtual client  206  (2) requests the disk data (e.g., location information) of the virtual client snapshot  312  from the proxy client  204 . The disk data of the virtual client snapshot  312 , or snapshot disk data, can include location information, such as an address, array, partition, block, tape location, cluster, etc., regarding where the virtual client snapshot  312  is located. As mentioned previously, the virtual client  206  and proxy client  204  can communicate via their respective data agents  212 ,  210 . 
     The proxy client  204  can use the information related to the virtual client, such as a virtual client identifier and/or a snapshot identifier, to identify the virtual client storage  310  and (3) request the location information and/or other disk data of the virtual client snapshot  312 . The storage device  208  can use the received information to identify and (4) retrieve the snapshot location information and/or other disk data of the virtual client snapshot  312 . 
     Upon identifying and retrieving the snapshot disk data of the virtual client snapshot  312 , the storage device  208  (5) transmits the snapshot location information and/or other disk data to the proxy client  204 . The snapshot location information and/or other disk data can then be (6) transmitted from the proxy client  204  to the virtual client  206 . Upon receiving the snapshot disk data, the virtual client  206  can perform additional processes involving the location information and/or other disk data. For example, the virtual client  206  can (7) mount the snapshot, thereby allowing the virtual client  206  to have access to the data contained within the virtual client snapshot  312 . Upon mounting the snapshot, the virtual client  206  can (8) notify the storage manager  202  that the snapshot mount operation has been completed. 
     As mentioned previously, although  FIGS. 3A and 3B  are directed to state diagrams illustrative of the interaction between the various components of the storage network environment illustrated in  FIG. 2A , it is to be understood that similar diagrams can be made for  FIGS. 2B and 2C . For purposes of brevity, however, such diagrams have been omitted. The additional diagrams can be made with similar features and may contain variations. For example, a state diagram illustrating the interaction between the components of the illustrative embodiment of  FIG. 2C  can contain additional steps illustrating the interaction between proxy client  204 , server  234 , and storage device  208 . For example, requests from the client  204  can be sent to the server  234  and forwarded to the storage device  208 . Similarly data from the storage device  208  can be transmitted to the server  234  and on to the proxy client  204 . One of ordinary skill in the art will understand the various embodiments and modifications that can be made to the state diagrams  3 A and  3 B in order to illustrate the interaction between the components of the illustrative embodiments of  FIGS. 2B and 2C . 
       FIGS. 4-7  are flow diagrams illustrative of embodiments of routines implemented by a proxy client for requesting a storage device to perform one or more storage operations. 
       FIG. 4  is a flow diagram illustrative of an embodiment of a routine  400  implemented by a client proxy for requesting a storage device to perform one or more storage operations. One skilled in the relevant art will appreciate that the elements outlined for routine  400  can be implemented by one or more computing devices/components that are associated with the proxy client  204 . Accordingly, routine  400  has been logically associated as being generally performed by the proxy client  204 . However, the following illustrative embodiment should not be construed as limiting. 
     At block  402 , the proxy client receives a storage operation request for a client. The storage operation request can be received from a client such as a virtual client or a separate client device, or can be received from a storage manager on behalf of a client. Furthermore, a storage operation request can include a request to perform, or have performed, one or more storage operations. For example the storage operation request can include, but is not limited to any one or more of a snapshot creation, snapshot mount, and/or a reversion to a previous snapshot. The storage operation request can be received at regular intervals as determined by a storage policy, and can be received from the client, the storage manager, some other computing device and/or a user via wired or wireless communication protocols. In some embodiments, the clients do not have direct access to a storage device storing the data of the clients. In certain embodiments, the clients have limited access to the storage device, but do not have direct access to the storage device for requesting one or more storage operations. 
     At block  404 , the proxy client  204  transmits the storage operation request to a storage device. As mentioned previously, the storage device can include one or more disk arrays storing data related to the clients and the proxy client. In some embodiments, prior to transmitting the storage operation request, the proxy client  204  uses information regarding the client to determine the storage device and location within the storage device where the data associated with the client is stored, and transmits this information to the storage device. 
     At block  406 , the proxy client receives an indication of the completion of the storage operation from the storage device. The indication can include various pieces of information that can be used to verify that the storage operation has been completed. For example, the indication can include a snapshot identifier when a snapshot is created, a snapshot disk identifier when a snapshot is to be mounted to a client, and/or some other identifier when other storage operations are used. 
     At block  408 , the proxy client transmits relevant data to the client. The relevant data can include any one or more identifiers received from the storage device that can be used by the client to verify that the storage operation has completed successfully. Furthermore the relevant data can include additional information that can be used by the client to perform additional processes based on the identifiers received from the proxy client  204 . 
     Additional, fewer, or different blocks can be used to implement the process  400  without departing from the spirit and scope of the description. For example, in some embodiments the client can perform one or more processes using the relevant data received from the proxy client. Furthermore, although not illustrated, the storage manager can transmit a storage operation command to the client, which in turn can transmit a storage operation request to the proxy client. 
       FIG. 5  is a flow diagram illustrative of an embodiment of a routine  500  implemented by the client proxy  204  for requesting a snapshot creation from a storage device. One skilled in the relevant art will appreciate that the elements outlined for routine  500  can be implemented by one or more computing devices/components that are associated with the client proxy  204 . Accordingly, routine  500  has been logically associated as being generally performed by the proxy client  204 . However, the following illustrative embodiment should not be construed as limiting. 
     At block  502 , the proxy client  204  receives a snapshot request from a client. As mentioned previously, the client can be a virtual client instantiated on the proxy client  204 , a virtual client instantiated on a server or other device, or a distinct client separate from the proxy client  204 . The snapshot request can be received at regular intervals as determined by a storage policy, and can be received from the client, the storage manager, some other computing device and/or a user via wired or wireless communication protocols. 
     At block  504 , the proxy client  204  transmits a snapshot request to a storage device  208 . As mentioned previously, prior to transmitting the snapshot request, the proxy client  204  can identify one or more portions of the storage device  208  that contain the data associated with the client and transmit that data with the snapshot request. 
     Upon receiving the snapshot request, the storage device  208  performs the snapshot creation by performing a snapshot of the portion of the storage device  208  that includes the data from the client. The storage device  208  can generate a snapshot identifier for the created snapshot. The snapshot identifier can be a number, can be any alphanumeric symbol or other number or symbol used to uniquely identify the snapshot that is created by the storage device. 
     At block  506 , the proxy client  204  receives the snapshot identifier from the storage device identifying the snapshot that has been created. At block  508 , the proxy server transmits the relevant snapshot data to the client. The relevant snapshot data can include the snapshot identifier received from the storage device or additional information, such as time and date information or other information that can be used by the client to identify the snapshot that is created by the storage device and/or otherwise process the data. 
     Additional, fewer, or different blocks can be used to implement the process  500  without departing from the spirit or scope of the description. For example, the proxy client  204  can notify the storage manager directly that the snapshot has been created. In some embodiments, the proxy client  204  receives a notification that a snapshot has been created and generates the snapshot identifier for the client. In certain embodiments, the client generates the snapshot identifier and transmits it along with the snapshot request or after receiving the relevant data associated with the created snapshot. 
       FIG. 6  is a flow diagram illustrative of an embodiment of a routine  600  implemented by a client proxy  204  for requesting a snapshot mount of a snapshot to be mounted to a client. One skilled in the relevant art will appreciate that the elements outlined for routine  600  can be implemented in one or more computing/components that are associated with the proxy client  204 . Accordingly, routine  600  has been logically associated as being generally performed by the proxy client  204 . However, the following illustrative embodiment should not be construed as limiting. 
     At block  602 , the proxy client  204  receives a request to mount a particular snapshot to a client. The particular snapshot can be a snapshot that was previously created by a storage device  208 . In some embodiments, the request can be a request to review or read from a previously created snapshot. The request can be received from a storage manager  202 , a user, and/or directly from a client, such as virtual client  206 , client  220 , and/or virtual client  230 . 
     At block  604 , the proxy client  204  requests disk information (e.g., location information) of the particular snapshot that is to be mounted to the client from the storage device. The disk information requested can include a disk sector, array, partition, block, tape location, or other location information. In turn, the storage device can retrieve the location information and/or other disk data associated with the snapshot and transmit the location information and/or other disk data to the proxy client  204 , as illustrated in block  606 . As mentioned previously, the disk information can include location information as to the location within the data storage where the snapshot is located. Furthermore upon requesting the disk information associated with the snapshot from the storage device, the proxy client  204  can provide one or more snapshot identifiers to the storage device. 
     At block  608  the proxy client  204  transmits the disk information (e.g., location information) received from the storage device to the client. Additional, fewer, or different blocks can be used to implement the process  600  without departing from the spirit and scope of the description. For example, the client can use the disk information to mount the snapshot to itself and/or access the snapshot data. Furthermore, the client can notify the storage manager that the snapshot has been mounted. In addition, the client can unmount the snapshot as desired. 
       FIG. 7  is a flow diagram illustrative of an embodiment of routine  700  implemented by a client proxy for requesting a storage device to revert to a previous snapshot. One skilled in the relevant art will appreciate that the elements outlined for routine  700  can be implemented by one or more computing devices/components that are associated with the client proxy  204 . Accordingly, routine  700  has been logically associated as being generally performed by the client proxy  204 . However, the following illustrative embodiment should not be construed as limiting. 
     At block  702 , the proxy server receives a reversion request. As mentioned previously the reversion request can be received from clients, such as the virtual client  206 , client  220 , and virtual client  230 , the storage manager  202 , other storage managers, users, computing devices, and the like. A reversion request can include the information regarding a specific snapshot that is to be used to revert the data in the storage device  208 . For example, this reversion request can include an identifier of the specific snapshot that should be used for the reversion. The identifier can include location information, time and/or chronological information, and the like. 
     At block  704 , the proxy client  204  transmits the reversion request to the storage device  208 . Using the information received in the reversion request, the storage device  208  is reverts the data related to the client to a previous version. At block  706 , the proxy client  204  receives verification from the storage device  208  that the data has been reverted. 
     At block  708 , the proxy client  204  transmits relevant reversion data to the client  708 . The relevant reversion data can include an identifier of the snapshot used for the reversion, as well as additional information concerning the new state of the data in the storage device  208 , which snapshot was used, the date and time of the reversion, additional snapshots that may be used for additional reversions, and the like. 
     Additional, fewer or different blocks can be used to implement the process  700  without departing from the spirit and scope of the description. For example the client proxy can notify the storage manager  202  that the data has been reverted. 
     Terminology 
     Conditional language, such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or steps. Thus, such conditional language is not generally intended to imply that features, elements and/or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without user input or prompting, whether these features, elements and/or steps are included or are to be performed in any particular embodiment. 
     Depending on the embodiment, certain acts, events, or functions of any of the algorithms described herein can be performed in a different sequence, can be added, merged, or left out all together (e.g., not all described acts or events are necessary for the practice of the algorithms). Moreover, in certain embodiments, acts or events can be performed concurrently, e.g., through multi-threaded processing, interrupt processing, or multiple processors or processor cores or on other parallel architectures, rather than sequentially. 
     Systems and modules described herein may comprise software, firmware, hardware, or any combination(s) of software, firmware, or hardware suitable for the purposes described herein. Software and other modules may reside on servers, workstations, personal computers, computerized tablets, PDAs, and other devices suitable for the purposes described herein. Software and other modules may be accessible via local memory, via a network, via a browser, or via other means suitable for the purposes described herein. Data structures described herein may comprise computer files, variables, programming arrays, programming structures, or any electronic information storage schemes or methods, or any combinations thereof, suitable for the purposes described herein. User interface elements described herein may comprise elements from graphical user interfaces, command line interfaces, and other suitable interfaces. 
     Further, the processing of the various components of the illustrated systems can be distributed across multiple machines, networks, and other computing resources. In addition, two or more components of a system can be combined into fewer components. Various components of the illustrated systems can be implemented in one or more virtual machines, rather than in dedicated computer hardware systems. Likewise, the data repositories shown can represent physical and/or logical data storage, including, for example, storage area networks or other distributed storage systems. Moreover, in some embodiments the connections between the components shown represent possible paths of data flow, rather than actual connections between hardware. While some examples of possible connections are shown, any of the subset of the components shown can communicate with any other subset of components in various implementations. 
     Embodiments are also described above with reference to flow chart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products. Each block of the flow chart illustrations and/or block diagrams, and combinations of blocks in the flow chart illustrations and/or block diagrams, may be implemented by computer program instructions. Such instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the acts specified in the flow chart and/or block diagram block or blocks. 
     These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to operate in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the acts specified in the flow chart and/or block diagram block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operations to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the acts specified in the flow chart and/or block diagram block or blocks. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosure. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the described methods and systems may be made without departing from the spirit of the disclosure. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosure.