Patent Publication Number: US-8533161-B2

Title: Fixed content storage within a partitioned content platform, with disposition service

Description:
The subject matter herein includes material that is subject to copyright, and all such rights are reserved. 
     CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to application: 
     Ser. No. 11/638,252, filed Dec. 13, 2006, titled “Policy-based management of a redundant array of independent nodes;” 
     Ser. No. 11/675,224, filed Feb. 15, 2007, titled “Method for improving mean time to data loss (MTDL) in a fixed content distributed data storage;” and 
     Ser. No. 11/936,317, filed Nov. 7, 2007, titled “Fast primary cluster recovery.” 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates generally to techniques for highly available, reliable, and persistent data storage in a distributed computer network. 
     2. Description of the Related Art 
     A need has developed for the archival storage of “fixed content” in a highly available, reliable and persistent manner that replaces or supplements traditional tape and optical storage solutions. The term “fixed content” typically refers to any type of digital information that is expected to be retained without change for reference or other purposes. Examples of such fixed content include, among many others, e-mail, documents, diagnostic images, check images, voice recordings, film and video, and the like. The traditional Redundant Array of Independent Nodes (RAIN) storage approach has emerged as the architecture of choice for creating large online archives for the storage of such fixed content information assets. By allowing nodes to join and exit from a cluster as needed, RAIN architectures insulate a storage cluster from the failure of one or more nodes. By replicating data on multiple nodes, RAIN-type archives can automatically compensate for node failure or removal. Typically, RAIN systems are largely delivered as hardware appliances designed from identical components within a closed system. 
     BRIEF SUMMARY 
     A content platform (or “cluster”) that comprises a redundant array of independent nodes is logically partitioned. Using a web-based interface, an administrator defines one or more “tenants” within the cluster, wherein a tenant has a set of attributes: namespaces, administrative accounts, data access accounts, and a permission mask. A namespace is a logical partition of the cluster that serves as a collection of objects typically associated with at least one defined application. Each namespace has a private file system with respect to other namespaces. This approach enables a user to segregate cluster data into logical partitions. Using the administrative interface, a namespace associated with a given tenant is selectively configured without affecting a configuration of at least one other namespace in the set of namespaces. One configuration option is a “disposition service” that, once enabled for a namespace, automatically deletes objects that were once under retention and whose retention time has expired. Preferably, the disposition service deletes objects that do not have a “retention hold” associated therewith. The service enables the content platform to automatically reclaim cluster capacity while minimizing external involvement and archive load. 
     The foregoing has outlined some of the more pertinent features of the invention. These features should be construed to be merely illustrative. Many other beneficial results can be attained by applying the disclosed invention in a different manner or by modifying the invention as will be described. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified block diagram of a fixed content storage archive in which the present invention may be implemented; 
         FIG. 2  is a simplified representation of a redundant array of independent nodes each of which is symmetric and supports an archive cluster application according to the present invention; 
         FIG. 3  is a high level representation of the various components of the archive cluster application executing on a given node; 
         FIG. 4  illustrates how a cluster is partitioned according to the techniques described herein; 
         FIG. 5  illustrates an Overview page of a tenant administrator console; 
         FIG. 6  illustrates a Namespace page of the tenant administrator console; 
         FIG. 7  illustrates a Create Namespace container page of the tenant administrator console; 
         FIG. 8  illustrates a Namespace Overview container page for a given namespace; 
         FIG. 9  illustrates a Policies container page for the given namespace by which the administrator can configure a given policy; 
         FIG. 10  illustrates how an administrator enables versioning for the namespace; 
         FIG. 11  illustrates how an administrator enables a disposition service for the namespace; 
         FIG. 12  illustrates how an administrator enables a privileged delete option for the namespace; and 
         FIG. 13  illustrates how an administrator enables retention classes for the namespace. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     It is known to provide a scalable disk-based archival storage management system, preferably a system architecture based on a redundant array of independent nodes. The nodes may comprise different hardware and thus may be considered “heterogeneous.” A node typically has access to one or more storage disks, which may be actual physical storage disks, or virtual storage disks, as in a storage area network (SAN). The archive cluster application (and, optionally, the underlying operating system on which that application executes) that is supported on each node may be the same or substantially the same. In one illustrative embodiment, the software stack (which may include the operating system) on each node is symmetric, whereas the hardware may be heterogeneous. Using the system, as illustrated in  FIG. 1 , enterprises can create permanent storage for many different types of fixed content information such as documents, e-mail, satellite images, diagnostic images, check images, voice recordings, video, and the like, among others. These types are merely illustrative, of course. High levels of reliability are achieved by replicating data on independent servers, or so-called storage nodes. Preferably, each node is symmetric with its peers. Thus, because preferably any given node can perform all functions, the failure of any one node has little impact on the archive&#39;s availability. 
     As described in U.S. Pat. No. 7,155,466, a distributed software application executed on each node captures, preserves, manages, and retrieves digital assets. In an illustrated embodiment of  FIG. 2 , a physical boundary of an individual archive is referred to as a cluster. Typically, a cluster is not a single device, but rather a collection of devices. Devices may be homogeneous or heterogeneous. A typical device is a computer or machine running an operating system such as Linux. Clusters of Linux-based systems hosted on commodity hardware provide an archive that can be scaled from a few storage node servers to many nodes that store thousands of terabytes of data. This architecture ensures that storage capacity can always keep pace with an organization&#39;s increasing archive requirements. Preferably, data is replicated across the cluster so that the archive is always protected from device failure. If a disk or node fails, the cluster automatically fails over to other nodes in the cluster that maintain replicas of the same data. 
     An illustrative cluster preferably comprises the following general categories of components: nodes  202 , a pair of network switches  204 , power distribution units (PDUs)  206 , and uninterruptible power supplies (UPSs)  208 . A node  202  typically comprises one or more commodity servers and contains a CPU (e.g., Intel x86, suitable random access memory (RAM), one or more hard drives (e.g., standard IDE/SATA, SCSI, or the like), and two or more network interface (NIC) cards. A typical node is a 2U rack mounted unit with a 2.4 GHz chip, 512 MB RAM, and six (6) 200 GB hard drives. This is not a limitation, however. The network switches  204  typically comprise an internal switch  205  that enable peer-to-peer communication between nodes, and an external switch  207  that allows extra-cluster access to each node. Each switch requires enough ports to handle all potential nodes in a cluster. Ethernet or GigE switches may be used for this purpose. PDUs  206  are used to power all nodes and switches, and the UPSs  208  are used to protect all nodes and switches. Although not meant to be limiting, typically a cluster is connectable to a network, such as the public Internet, an enterprise intranet, or other wide area or local area network. In an illustrative embodiment, the cluster is implemented within an enterprise environment. It may be reached, for example, by navigating through a site&#39;s corporate domain name system (DNS) name server. Thus, for example, the cluster&#39;s domain may be a new sub-domain of an existing domain. In a representative implementation, the sub-domain is delegated in the corporate DNS server to the name servers in the cluster itself. End users access the cluster using any conventional interface or access tool. Thus, for example, access to the content platform may be carried out over any protocol (REST, HTTP, FTP, NFS, AFS, SMB, a Web service, or the like), via an API, or through any other known or later-developed access method, service, program or tool. 
     Client applications access the cluster through one or more types of external gateways such as standard UNIX file protocols, or HTTP APIs. The archive preferably is exposed through a virtual file system that can optionally sit under any standard UNIX file protocol-oriented facility. These include: NFS, FTP, SMB/CIFS, or the like. 
     In one embodiment, the archive cluster application runs on a redundant array of independent nodes (H-RAIN) that are networked together (e.g., via Ethernet) as a cluster. The hardware of given nodes may be heterogeneous. For reliability, however, preferably each node runs an instance  300  of the distributed application (which may be the same instance, or substantially the same instance), which is comprised of several runtime components as now illustrated in  FIG. 3 . Thus, while hardware may be heterogeneous, the software stack on the nodes (at least as it relates to the present invention) is the same. These software components comprise a gateway protocol layer  302 , an access layer  304 , a file transaction and administration layer  306 , and a core components layer  308 . The “layer” designation is provided for explanatory purposes, as one of ordinary skill will appreciate that the functions may be characterized in other meaningful ways. One or more of the layers (or the components therein) may be integrated or otherwise. Some components may be shared across layers. 
     The gateway protocols in the gateway protocol layer  302  provide transparency to existing applications. In particular, the gateways provide native file services such as NFS  310  and SMB/CIFS  312 , as well as a Web services API to build custom applications. HTTP support  314  is also provided. The access layer  304  provides access to the archive. In particular, according to the invention, a Fixed Content File System (FCFS)  316  emulates a native file system to provide full access to archive objects. FCFS gives applications direct access to the archive contents as if they were ordinary files. Preferably, archived content is rendered in its original format, while metadata is exposed as files. FCFS  316  provides conventional views of directories and permissions and routine file-level calls, so that administrators can provision fixed-content data in a way that is familiar to them. File access calls preferably are intercepted by a user-space daemon and routed to the appropriate core component (in layer  308 ), which dynamically creates the appropriate view to the calling application. FCFS calls preferably are constrained by archive policies to facilitate autonomous archive management. Thus, in one example, an administrator or application cannot delete an archive object whose retention period (a given policy) is still in force. 
     The access layer  304  preferably also includes a Web user interface (UI)  318  and an SNMP gateway  320 . The Web user interface  318  preferably is implemented as an administrator console that provides interactive access to an administration engine  322  in the file transaction and administration layer  306 . The administrative console  318  preferably is a password-protected, Web-based GUI that provides a dynamic view of the archive, including archive objects and individual nodes. The SNMP gateway  320  offers storage management applications easy access to the administration engine  322 , enabling them to securely monitor and control cluster activity. The administration engine monitors cluster activity, including system and policy events. The file transaction and administration layer  306  also includes a request manager process  324 . The request manager  324  orchestrates all requests from the external world (through the access layer  304 ), as well as internal requests from a policy manager  326  in the core components layer  308 . 
     In addition to the policy manager  326 , the core components also include a metadata manager  328 , and one or more instances of a storage manager  330 . A metadata manager  328  preferably is installed on each node. Collectively, the metadata managers in a cluster act as a distributed database, managing all archive objects. On a given node, the metadata manager  328  manages a subset of archive objects, where preferably each object maps between an external file (“EF,” the data that entered the archive for storage) and a set of internal files (each an “IF”) where the archive data is physically located. The same metadata manager  328  also manages a set of archive objects replicated from other nodes. Thus, the current state of every external file is always available to multiple metadata managers on several nodes. In the event of node failure, the metadata managers on other nodes continue to provide access to the data previously managed by the failed node. This operation is described in more detail below. The storage manager  330  provides a file system layer available to all other components in the distributed application. Preferably, it stores the data objects in a node&#39;s local file system. Each drive in a given node preferably has its own storage manager. This allows the node to remove individual drives and to optimize throughput. The storage manager  330  also provides system information, integrity checks on the data, and the ability to traverse local directory structures. 
     As illustrated in  FIG. 3 , the cluster manages internal and external communication through a communications middleware layer  332  and a DNS manager  334 . The infrastructure  332  is an efficient and reliable message-based middleware layer that enables communication among archive components. In an illustrated embodiment, the layer supports multicast and point-to-point communications. The DNS manager  334  runs distributed name services that connect all nodes to the enterprise server. Preferably, the DNS manager (either alone or in conjunction with a DNS service) load balances requests across all nodes to ensure maximum cluster throughput and availability. 
     In an illustrated embodiment, the application instance executes on a base operating system  336 , such as Red Hat Linux 10.0. The communications middleware is any convenient distributed communication mechanism. Other components may include FUSE (Filesystem in USErspace), which may be used for the Fixed Content File System (FCFS)  316 . The NFS gateway  310  may be implemented by Unfsd, which is a user space implementation of the standard nfsd Linux Kernel NFS driver. The database in each node may be implemented, for example, by PostgreSQL (also referred to herein as Postgres), which is an object-relational database management system (ORDBMS). The node may include a Web server, such as Jetty, which is a Java HTTP server and servlet container. Of course, the above mechanisms are merely illustrative. 
     The storage manager  330  on a given node is responsible for managing the physical storage devices. Preferably, each storage manager instance is responsible for a single root directory into which all files are placed according to its placement algorithm. Multiple storage manager instances can be running on a node at the same time, and each usually represents a different physical disk in the system. The storage manager abstracts the drive and interface technology being used from the rest of the system. When the storage manager instance is asked to write a file it generates a full path and file name for the representation for which it will be responsible. In a representative embodiment, each object to be stored on a storage manager is received as raw data to be stored, with the storage manager then adding its own metadata to the file as it stores it to keep track of different types of information. By way of example, this metadata includes: EF length (length of external file in bytes), IF Segment size (size of this piece of the Internal File), EF Protection representation (EF protection mode), IF protection role (representation of this internal file), EF Creation timestamp (external file timestamp), Signature (signature of the internal file at the time of the write (PUT), including a signature type) and EF Filename (external file filename). Storing this additional metadata with the internal file data provides for additional levels of protection. In particular, scavenging can create external file records in the database from the metadata stored in the internal files. Other services (sometimes referred to herein as “policies”) can validate internal file hash against the internal file to validate that the internal file remains intact. 
     As noted above, internal files preferably are the “chunks” of data representing a portion of the original “file” in the archive object, and preferably they are placed on different nodes to achieve striping and protection blocks. Typically, one external file entry is present in a metadata manager for each archive object, while there may be many internal file entries for each external file entry. Typically, internal file layout depends on the system. In a given implementation, the actual physical format of this data on disk is stored in a series of variable length records. 
     The request manager  324  is responsible for executing the set of operations needed to perform archive actions by interacting with other components within the system. The request manager supports many simultaneous actions of different types, is able to roll-back any failed transactions, and supports transactions that can take a long time to execute. The request manager also ensures that read/write operations in the archive are handled properly and guarantees all requests are in a known state at all times. It also provides transaction control for coordinating multiple read/write operations across nodes to satisfy a given client request. In addition, the request manager caches metadata manager entries for recently used files and provides buffering for sessions as well as data blocks. 
     A cluster&#39;s primary responsibility is to store an unlimited number of files on disk reliably. A given node may be thought of as being “unreliable,” in the sense that it may be unreachable or otherwise unavailable for any reason. A collection of such potentially unreliable nodes collaborate to create reliable and highly available storage. Generally, there are two types of information that need to be stored: the files themselves and the metadata about the files. 
     A content platform such as described above may implement a data protection level (DPL) scheme such as described in Ser. No. 11/675,224, filed Feb. 15, 2007, the disclosure of which is incorporated by reference. 
     The content platform also may implement a replication scheme such as described in Ser. No. 11/936,317, filed Nov. 7, 2007, the disclosure of which is incorporated by reference. 
     The above is a description of a known content platform or “cluster.” The following describes how an enterprise (or other entity, such as a service provider) can partition such a cluster and use the cluster resources more effectively as the amount of user data to be stored increases. 
     Cluster Partitioning—Tenants and Namespaces 
     The following terminology applies to the subject matter that is now described: 
     Data Account (DA): an authenticated account that provides access to one or more namespaces. The account has a separate set of CRUD (create, read, update, and delete) privileges for each namespace that it can access. 
     Namespace (NS): a logical partition of the cluster. A namespace essentially serves as a collection of objects particular to at least one defined application. As will be described, each namespace has a private filesystem with respect to other namespaces. Moreover, access to one namespace does not grant a user access to another namespace. An archive may have an upper bound on the number of namespaces allowed on a single cluster (e.g., up to 100). 
     Authenticated Namespace (ANS): a namespace (preferably HTTP-only) that requires authenticated data access. 
     Default Namespace (dNS): a namespace for use with data that is ingested into the cluster in other than REST (Representational State Transfer), where REST is a lightweight protocol commonly used for exchanging structured data and type information on the Web. Further, even if an application uses the REST interface, if a namespace is not specified during authentication to the cluster, all data can be stored in the default namespace. 
     Tenant: a grouping of namespace(s) and possibly other subtenants. 
     Top-Level Tenant (TLT): a tenant which has no parent tenant, e.g. an enterprise. 
     Subtenant: a tenant whose parent is another tenant; e.g. the enterprise&#39;s financing department. 
     Default Tenant: the top-level tenant that contains only the default namespace. 
     Cluster: a physical archive instance, such as described above. 
     When the cluster is freshly installed, it contains no tenants. Cluster administrators create top-level tenants and administrative accounts associated with those top-level tenants, as well as enable the default tenant and default namespace.  FIG. 4  illustrates this basic concept. As shown there, there is a cluster instance  400 , such as the system illustrated in  FIGS. 2-3  and described above. As will be illustrated in more detail below, a cluster administrator has an account  402 . An appropriate administrator is given authority to create a top level tenant  404 , and one or more namespaces for that TLT, such as first authenticated namespace  406  (for an engineering department) and a second authenticated namespace  408  (for a finance department). An appropriate administrator also sets up administrator accounts  412  and data accounts  414  for the TLT. In addition, an administrator can also enable a default tenant  416  having an associated default namespace  418 . Although not shown, authorized administrators may also set up subtenants. The administrator also establishes administrative logs  420 . Of course, the above configuration is merely exemplary, as the subject matter herein is not limited to any particular type of use case or tenant/namespace configuration. 
     At a macro level, all namespaces can be considered as the same or substantially the same entities with the same qualities and capabilities. Generally, and as will be seen, a namespace has a set of associated capabilities that may be enabled or disabled as determined by an appropriately credentialed administrator. A single namespace can host one or more applications, although preferably a namespace is associated with just one defined application (although this is not a limitation). A namespace typically has one or more of the following set of associated capabilities that a namespace administrator can choose to enable or disable for a given data account: read (r)—includes reading files, directory listings, and exists/HEAD operations; write (w); delete (d); purge (p)—allows one to purge all versions of a file; privileged (P)—allows for privileged delete and privileged purge; and search (s). 
     Using namespaces, and as illustrated generally in  FIG. 4 , an administrator can create multiple domains for a cluster, which domains differ based upon the perspective of the user/actor. These domains include, for example, the following: access application, cluster admin, TLT admin, subtenant admin, and replication. The domain of the access application is a given namespace. An authorized administrator (such as admin  402 ) has a view of the cluster as whole. As shown, the administrator  402  can create a top-level tenant and perform all of the administration for actions that have cluster scope. In certain situations, such as enterprise deployments, the tenant may grant appropriate administrators the ability to manage the tenant, in which case any cluster admin also will be able to function as a TLT admin. The TLT admin creates namespaces, data accounts and subtenants. The TLT is able to modify some configuration settings, such as namespace quotas or to enable versioning. The subtenant admin is able to create a namespace under a subtenant. The domain of replication is a set of TLTs defined by the cluster administrator while configuring replication between clusters. 
     One of ordinary skill in the art will appreciate that a tenant is a logical archive as viewed by an administrator. As shown in  FIG. 4 , a tenant may represent an organization or a department using a portion of a cluster. A tenant may be implemented as a hierarchy in that it can contain other tenants. 
     A tenant preferably has a set of attributes: namespaces, administrative accounts, data access accounts, permission mask, roll-up of state, name, and quotas. A tenant may contain zero or more namespaces. A tenant will have a set of administrative accounts (such as account  412 ) that enable users to monitor and update attributes of the tenant. The data access accounts are the set of accounts which access namespace objects. A permission mask (r/w/d/p/P/s) is the set of permissions global to the tenant and that mask a namespace&#39;s permissions. The roll-up of state are the metrics on all namespaces within the tenant. The name of the tenant is settable and changeable by an appropriate administrator. Tenant names within the same cluster must not collide. A top level tenant preferably is assigned a hard storage quota by the administrator. The appropriate admin can lower or raise that quota, and he or she can assign as much quota as desired. The TLT can also specify a soft quota, which is a given percentage of the hard quota. A tenant is able to divide its quota among one or more namespaces, but the total assigned quota may not exceed that of the tenant. For accounting purposes, preferably the quota will measure the rounded up size of an ingested file to the nearest block size. A soft quota is typically a predetermined percentage (e.g., 85%) of a hard quota, but this value may be configurable. Once the hard quota is exceeded, no further writes are allowed, although in-progress writes preferably are not blocked. It may be acceptable to have a delay between exceeding a quota and having future writes blocked. Preferably, quotas are replicated but cannot be changed. When a replica becomes writable, the quota is enforced there as well. 
     A tenant administrator also has a set of roles that include one or more of the following: a monitor role, an administrator role, a security role, and a compliance role. A monitor role is a read-only version of an administrator role. The administrator role is the primary role associated with a tenant. As described and illustrated above, this role allows an admin user to create namespaces under the current tenant, and it provides a view of all namespaces within this tenant (and associated statistics such as file counts, space available, space used, etc.). The administrator also can view tenant and namespace logs, and he or she can view/update tenant and namespace configuration. The security role gives a user the ability to create/modify/delete new administrative users. A user with the security role can add and delete roles from other tenant-level administrative accounts. When the tenant is first created, preferably there is one administrative user associated with the tenant, and this user account has just the security role. The compliance role enables privileged delete and retention class functions (as defined below). 
     A namespace is a logical archive as viewed by an application. According to the subject matter herein, a particular namespace is distinct from a different namespace, and access to one namespace does not grant a user access to another namespace. Preferably, administration of a namespace is performed at the owning tenant level. Moreover, preferably a namespace may only be deleted if a count of objects associated with that namespace is zero. A namespace preferably also has the following attributes: permission mask, initial settings, other settings, display name, quota, logs, and stats. As noted above, the permission mask (r/w/d/p/P/s) is the set of settings global to the namespace and which mask an account&#39;s permissions. The initial settings identify a data protection level (DPL), a hashing scheme, and the like, that preferably remain persistent. The other settings refer to settings (such as retention, shred, versioning, indexing, and the like) that can be set on the namespace and then later changed. This feature is described in more detail below. The display name is a name or other identifier for the namespace. The quota is either hard (in GB) or soft (in percent). The logs attribute identifies the system events related to the namespace that will be logged. The stats attribute identifies the statistics that are generated from namespace-related data, such as capacity, number of objects, and the like. 
     Preferably, tenant names and namespace names are human readable identifiers in the various administrative user interfaces (UIs). Preferably, these names also are used in hostnames to specify the namespace of a data access request, the tenant which an administrator is administrating, and the scope over which a search should be confined. The namespace name is useful because a tenant may have more than one namespace associated with it. Preferably, object access over HTTP uses a hostname in the form of:
         &lt;namespace-name&gt;.&lt;tenant-name&gt;.&lt;cluster-domain-suffix&gt;
 
These names comply with conventional domain name system (DNS) standards. As noted above, tenant names on a cluster must not collide.
       

     The following provides additional details of a tenant administrative user interface (UI) and the associated functionality provided by that interface. Preferably, the tenant UI is implemented as a Web-based user interface (such as the interface  318  in  FIG. 3 ), namely, as a tenant administrator console that provides interactive access to an administration engine. The administrative console preferably is a password-protected, Web-based GUI that provides a dynamic view of the archive. Once the tenant administrator has logged into the tenant administrator console, an overview page is provided that presents a main navigation menu. That menu provides access to one or more high level functions (implemented as web pages) such as Overview, Namespaces, Data Access Accounts, Services, Security and Monitoring. Several of these interfaces are now described in more detail. 
     As seen in  FIG. 5 , the Overview page  500  shows information about the current tenant (i.e., the tenant the administrator logged into), including statistics and major event logs. Typically, the page contains the following information, and preferably this information is not editable: tenant name  502 , a link  504  to update the tenant account settings, a checkbox  506  which allows any cluster administrator to also administer this tenant and search over all objects in all namespaces associated with this tenant (provided they have a search role), rolled-up information  508  such as quota (total, unallocated and allocated), namespaces (total number, objects ingested, objected indexed and objects versioned), and accounts (number of data accounts, and number of administer accounts), a permissions menu  510  applied to namespaces owned by the tenant, a tenant description  512 , and logs and alerts  514 . As illustrated in  FIG. 5 , the permissions menu identifies the effective permissions (which are checked), and the values of the permissions mask. Because this is the top level, all the settings are shown as inherited and as present in the tenant mask. If the user selects the edit tab, a sub-menu  516  is displayed to enable a permitted administrator to modify the individual permissions. Preferably, the administrator role can modify panels on this page, and the monitor and administrator roles can view the page and panels on the page. 
       FIG. 6  illustrates the Namespaces page  600 , which lists all namespaces defined directly under this tenant, as well as general statistics about each (object count, any alerts, and quota). This page allows the administrator to drill down for further configuration of a specific namespace. This page is viewable by accounts with the administrator and monitor roles. The page includes a table  602  listing the namespaces owned by the current tenant, and controls (e.g., links/buttons  604 ) are provided to enable the administrator to create a namespace, view or edit the settings for a listed namespace, or view statistics for a listed namespace. The table includes columns in which statistics and other information for a given namespace, such as object count  606 , alerts  608  and quota  610 , are displayed in summary form. 
     By selecting the Create Namespace container title bar, the Create Namespace container  700  expands as shown in  FIG. 7  to allow a tenant to add a new namespace for the current tenant. To create a new namespace, the user provides the following information: name  702 , description  704 , maximum size (the hard quota in TB, GB, MB, or the like, for the new namespace)  706 , a soft quota (may default to 85%)  708 , a DPL value  710  (may default to 1 for external storage, 2 for internal storage), a hash value  712  (may default to SHA-256), a retention mode  714  (enterprise or compliance, defaults to enterprise), object versioning  716  (on/off, defaults to off), and search indexing  718  (on/off, default value is inherited from the tenant). Preferably, the administrator role can view and modify this page. Once the individual parameters for the namespace are configured, the user selects the Create Namespace button  720  to complete the process. In this manner, each individual namespace within a tenant configuration is highly configurable as compared to any other namespace within the tenant. This namespace-by-namespace configurability option provides significant operational and management flexibility. 
     Referring back to  FIG. 6 , if the user selects any one of the identified Namespaces, a Namespace Overview container  800  expands as shown in  FIG. 8 , exposing statistics about the selected namespace. These include a field  802  for the namespace name, object and usage graphs  804  (e.g., the objects in namespace, objects indexed, usage such as bytes transferred into namespace, file size sum, and total quota allocated), alerts  806 , the permissions menu  808  (showing the permissions mask for this namespace), and a description  810 . The monitor and administrator roles can view this page. As also illustrated in  FIG. 8 , once a given Namespace is selected for configuration, a number of container pages are exposed including a Policies tab  812 , a Services tab  814 , a Compliance tab  816 , a Protocols tab  818 , and a Monitoring tab  820 . Several of these interfaces are now described in more detail. 
     If the user selects the Policies tab  812  from the Namespace Overview container  800 , a Policies page is displayed from which the user can then configure one or more policies for the particular namespace. In  FIG. 9 , the user has opened the Policies page  900  and selected a Retention policy title bar, which opens up a container  902  through which the administrator sets a retention policy. If an offset retention method  904  is selected, the administrator sets maximum values (years, months and days). If a fixed date retention method  906  is selected, the user uses the calendar to set a date. If a special values retention method  908  is selected, the user can select from a set of options: deletion allowed, initially unspecified, indefinite and prohibited. If a retention classes method  910  is selected, a set of additional options are exposed, as will be described in more detail below. Once the configuration is made, it is saved by selecting the Update Policy button  912 . 
     Another configurable policy is versioning.  FIG. 10  illustrates a container  1000  with a set of controls that can be used for this purpose. When the container is opened, the user can select a checkbox  1002  to enable versioning for this particular namespace. If this checkbox is selected, the user can then configure (using field  1004 ) how long the versions are to be kept on the primary cluster and, if replication is enabled, on any replica cluster. This policy is saved by selecting the Update Policy button  1006 . 
     Returning to the description of the administrator console, if the user selects the Services tab  814  for the Namespace, one or more service options may be configured. One such service option is disposition (sometimes referred to as a “disposition service”), which enables automatic deletion of objects with expired retention. The disposition service option is enabled through a panel  1100  that includes a checkbox  1102 , which is selected to enable the option for the particular namespace. The user selects the Update Services button  1104  to complete the configuration. Thus, according to the configuration option, once the configured retention (e.g., identified in the retention class) expires, the objects associated with that retention class (for this namespace only) are automatically deleted from the cluster. This operation is advantageous as it enables the cluster to reclaim storage space. The disposition service, however, is configurable on a tenant or namespace basis, which is highly desirable and provides increased management flexibility. The disposition service can be configured in association with a retention class, and such classes are configurable at a tenant level, which allows tenant administrators to finely control disposition of the tenant&#39;s namespaces. 
     The following provides additional details regarding the disposition service. As noted above, the service works to automatically delete from the platform so-called “expired objects,” namely, an object where the retention period has expired and the retention is not zero (current time&gt;retention time&gt;0). Thus, the disposition service performs work on committed files with set retention values. When the service runs, eligible expired objects are located and deleted. Preferably, the following objects are not candidates for disposition: objects not under retention (i.e. retention is not set on the object), objects under retention hold, and objects belonging to a cluster or namespace that has deletes disabled. Thus, for objects under retention hold, or where deletes or disabled, the disposition operation, in effect, is overridden, until the particular condition clears or is otherwise inapplicable to the object under retention. Also, files with zero retention (delete-able now) are not deleted. Objects deleted by the disposition service are treated by the system as conventional deletes (and removed from a search index and replicated), and the deletions are logged and reported as disposition service metrics. 
     The disposition service is configured at the namespace level, as described and illustrated above. By default, the disposition service is disabled and then enabled by an administrator as a configuration. This is not a limitation of course. As an option, the service may provide a notification to an administrator indicating the object or objects that are coming due or are up for deletion (or that have been deleted), and the interface may provide a web page from which information about such objects can be viewed. 
     As noted above, a new version of the data object is created upon ingestion into the namespace of another data object having a same file name as the data object. Preferably, the disposition service only services the current version of any object in the namespace. As described below, another namespace configuration option is the ability to configure one or more Retention Classes, where a retention class is a defined grouping of objects that are to be subject to a same retention configuration. The configuration of whether an object should be auto-deleted by the disposition service may be a property of a retention class, in which case a “dispose on expiration” column is added to the retention class configuration page. 
     Although not meant to be limiting, preferably the disposition service runs periodically (e.g., nightly) on a given region per storage node. 
     If the user selects the Compliance tab  816  for the Namespace, one or more compliance options may be configured. In  FIG. 12 , the user has selected a Privileged Delete compliance option, by which the user can identify for deletion a particular object and provide reasons for this deletion. As shown, the Privileged Delete panel  1200  includes a field  1202  in which the object to be deleted is identified (preferably by its full path), as well as a description  1204  field indicating the reason for deletion. By selecting the Delete This Object button  1206 , the object is then permanently deleted from the cluster. Preferably, this feature is only enabled for an enterprise mode of operation. The Privileged Delete function enables the user to remove all versions of an object, even if the object is under retention. 
     Another configurable option in the Compliance tab  816  for the Namespace is the option to configure one or more Retention Classes. A Retention Class is a defined grouping of objects that are to be subject to the same retention configuration. When the user navigates to the Retention Classes tab, a set of previously-defined Retention Classes and their values are displayed and can be selected for review. To add a new retention class, the user selects a title bar, which opens up the container  1300  shown in  FIG. 13 . Using this panel, the user can identify the new retention class name using field  1302 , select the retention method by menu  1304 , and add a description in field  1306 . The retention method menu  1304  exposes the retention options (years, months, and days) previously described. The Add new retention class button  1308  is used to configure the new class. 
     Although not illustrated in detail, the other display panels expose other configuration options that may be used to configure operations and functions on a namespace-specific basis. Thus, Protocols tab  818  enables the administrator to manage protocol settings, such as enabling HTTP, HTTPS, and to create white/block lists of IP addresses. The Monitoring tab  820  enables the administrator to identify or review system log messages that are specific to the namespace, to review object status, and to illustrate privileged delete and retention class activities. 
     The administrator can also create and manage data access accounts from pages in the console and have these configuration settings applied to all namespaces for which the tenant is currently logged into. For each such data access account, the administrator can associate the desired access rights (e.g., read, write, delete, purge, search, etc.) that will be afforded the individual. 
     If the namespace is authenticated, the following additional controls may be imposed. Preferably, access to archive objects in an authenticated namespace is carried out through HTTP and subject to valid credentials. A client must supply these credentials to the cluster, typically using Cookie and Host headers on each HTTP operation. The necessary information required to map a client request to a specific data access account in a namespace includes username, password, and a fully qualified namespace name (FQNN). The FQNN identifies the namespace within a tenant hierarchy, and it is based on the namespace name, the tenant name, and a tenant&#39;s parent name (if any). REST access methods preferably are used for object actions (object ingestion, object retrieval, object existence checks, object deletion, object purge, directory listing, and directory creation), and metadata actions (set retention, set legal hold, set shred on delete, set/get/delete custom metadata, get all metadata). As is known, REST (Representational State Transfer) is a lightweight XML-based protocol commonly used for exchanging structured data and type information on the Web. Transport layer security mechanisms, such as HTTP over TLS (Transport Layer Security), may be used to secure messages between two adjacent nodes. Familiarity with these technologies and standards is presumed. 
     Thus, e.g., an HTTP DELETE request is used to delete a data object or empty data directory from a namespace. If versioning is enabled for the namespace, this method deletes the most current version of a data object, or it can purge all versions of an object. If a data account has the compliance permission enabled, this method may privilege delete or privilege purge an object under retention, as described above. The HTTP DELETE request preferably supports a set of metadata parameters such as: purge (true/false), which controls whether to delete all versions (if the object is versioned); privileged (true/false), which controls whether this is a privileged delete or privileged purge of an object under retention, and reason, which is set to true (if privileged) and provides an HTTP 400 error (if not). 
     By partitioning the UI into cluster and tenant-focused pieces, different people can perform cluster and tenant management. This ensures that privacy between the cluster admin and tenant admin views is enforced, ensures that the tenant does not have access to hardware or other details that may “break” the cluster, and protects the privacy of tenant data. 
     The subject matter described herein provides numerous advantages. Using the namespaces approach described, an entity (such as an enterprise operating the archive) can more easily segregate and manage its data. The approach enables the administrator to perform cluster operations on select subsets of the total cluster data set, as well as the ability to perform metering operations (e.g., capacity reporting) at a finer granularity. The ability to partition the cluster in the manner described provides significant operational, management and administrative efficiencies, as the ever-increasing (e.g., petabyte scale) data would be difficult to manage otherwise. 
     The described subject matter enables different administrators to perform cluster and tenant management, and to minimize the information that passes between these two areas. 
     The subject matter is not limited to any particular type of use case. A typical use environment is an enterprise, although the techniques may be implemented by a storage service provider or an entity that operates a storage cloud. 
     The techniques described herein, wherein users associated with a tenant (such as a TLT) have access privileges created and managed as set forth above may be extended and used in other than an archive cluster for fixed content. Thus, for example, these techniques may also be implemented in the context of a standard virtualization approach for a storage management system. 
     While the above describes a particular order of operations performed by certain embodiments of the invention, it should be understood that such order is exemplary, as alternative embodiments may perform the operations in a different order, combine certain operations, overlap certain operations, or the like. References in the specification to a given embodiment indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. 
     While the present invention has been described in the context of a method or process, the present invention also relates to apparatus for performing the operations herein. This apparatus may be specially constructed for the required purposes, or it may comprise a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a computer readable storage medium, such as, but is not limited to, any type of disk including optical disks, CD-ROMs, and magnetic-optical disks, read-only memories (ROMs), random access memories (RAMs), magnetic or optical cards, or any type of media suitable for storing electronic instructions, and each coupled to a computer system bus. 
     While given components of the system have been described separately, one of ordinary skill will appreciate that some of the functions may be combined or shared in given instructions, program sequences, code portions, and the like. 
     As used herein, the word “location” is not necessarily limited to a “geographic” location. While clusters are typically separated geographically, this is not a requirement. A primary cluster may be located in one data center in a city, while the replica cluster is located in another data center in the same center. The two clusters may also be in different locations within a single data center. 
     Although the present invention has been described in the context of an archive for “fixed content,” this is not a limitation either. The techniques described herein may be applied equally to storage systems that allow append and replace type modifications to the content.