Abstract:
Snapshot sets comprising snapshot criteria are created, maintained, and executed via a command set designed to facilitate managing and conducting snapshots on data distributed across multiple volumes. Snapshot criteria such as source volume, target volume, redundancy level, copy mode, and the like are added as desired to a snapshot set. Upon invocation of an execute command, the fast replication operations defined by the snapshot set are executed, providing a logically atomic data replication utility potentially involving multiple sources and targets. In one embodiment auto selection of a target may be specified, thus facilitating over-subscription of target resources. The present invention reduces the complexity of archiving data—particularly data distributed across multiple volumes such as data associated with database applications and the like.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. The Field of the Invention  
         [0002]     The invention relates to methods, devices, and systems for archiving data. Specifically, the invention relates to methods, devices, and systems for managing and conducting fast replication operations within storage sub-systems.  
         [0003]     2. The Relevant Art  
         [0004]     Data processing systems often work with large amounts of data and require means and methods to manage the storage and archiving of that data. For example, transaction processing systems typically access large databases and log results such as transaction records at a very high rate. The ability to quickly and reliably copy data from one storage area to another enables the deployment of efficient and reliable high-performance processing applications and systems.  
         [0005]     Fast replication techniques such as IBM&#39;s flashcopy technology have been developed in response to the need for efficient copying mechanisms within high-performance processing systems. A fast replication operation gives the appearance of an instantaneous copy while the actual transfer of data is conducted as a background process, or deferred until the data to be copied is about to be overwritten. With fast replication techniques, applications may conduct data snapshots (point-in-time copies) and continue processing rather than suspending operation while the data transfers occur.  
         [0006]     In addition to increased performance, fast replication capable systems simplify the code complexity of I/O intensive processes such as those conducted on large mainframe systems and the like. For example, fast replication techniques relieve applications from error prone memory management and housekeeping tasks. System performance may also be increased in that support for fast replication operations may be provided by low-level drivers and devices that are optimized for performance.  
         [0007]     Fast replication capable systems often support multiple concurrent fast replication data transfers. Since the data transfer may be deferred indefinitely, the act of initiating a fast replication operation between a source and a target volume is often referred to as “establishing a fast replication relationship.” Likewise, canceling a pending fast replication transfer may be referred to as “withdrawing a fast replication relationship.” 
         [0008]     Without support for fast replication relationships, conducting a point-in-time copy often requires that a system suspend all tasks that access a source and/or target device. Since many systems do not have explicit knowledge of the devices that will be accessed by each task, those systems require suspension of all tasks except for the task conducting the actual fast replication operations. Suspension of the various tasks or processes in order to conduct fast replication operations greatly reduces the performance of multi-tasking systems.  
         [0009]     One challenge of fast replication capable systems, particularly those systems capable of establishing multiple simultaneous fast replication relationships on a sub-volume basis, is managing the many relationships that may be involved in creating a snapshot. Multiple applications or utilities may share a core set of data files that may be distributed across multiple volumes. Furthermore, each target volume in a fast replication relationship must be identified previous to establishing a relationship. Requiring each application or system utility to be aware of all the resources and relationships involved in conducting a snapshot creates a logistical nightmare for system administrators, application developers, and users.  
         [0010]     What is needed are means and methods for managing and conducting snapshot operations that reduce the programming and administrative burdens associated with snapshot operations, particularly snapshot operations involving data distributed across multiple volumes of a storage subsystem or network.  
       SUMMARY OF THE INVENTION  
       [0011]     The various elements of the present invention have been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available snapshot management methods. Accordingly, the present invention provides an improved method, apparatus, and system for managing and conducting snapshot operations.  
         [0012]     In one aspect of the present invention, a method for managing and conducting snapshot operations includes adding snapshot criteria to a snapshot set, and initiating a plurality of fast replication operations as specified by the snapshot set. The method may also include one or more operations selected from the following: creating the snapshot set, deleting a specified snapshot set, provide information regarding a specified snapshot set, deleting specified snapshot criteria from the snapshot set, and terminating the plurality of fast replications operation specified by the snapshot set.  
         [0013]     In one embodiment, the snapshot criteria is specified using a data structure containing a variety of data fields related to snapshot operations. In the aforementioned embodiment the data fields include, a source volume indicator, a target volume indicator, an auto-select target indicator, a partial volume indicator, a source extents indicator, a target extents indicator, a redundancy level indicator, and a background copy indicator. The ability to define criteria for snapshot (i.e. fast replication) operations reduces the programming burden associated with managing and conducting snapshot operations.  
         [0014]     In another aspect of the present invention, a programming interface for managing and conducting snapshot operations includes an Add to Snapshot Set function configured to add snapshot criteria to a snapshot set, and an Execute Snapshot Set function configured to initiate a plurality of fast replications operations as specified by the snapshot set. The programming interface may also include a Create Snapshot Set function configured to create a snapshot set, a Delete Snapshot Set function configured to delete a specified snapshot set, a Remove From Snapshot Set function configured to delete specified snapshot criteria from the snapshot set, a Get Snapshot Set function configured to provide information regarding a specified snapshot set, and a Terminate Snapshot Set function configured to terminate the plurality of fast replications operations specified by the snapshot set.  
         [0015]     The programming interface facilitates accessing the functionality of the present invention from an application, system utility or the like that may be external to the hardware executing the snapshot management methods of the present invention.  
         [0016]     In another aspect of the present invention, an apparatus for managing and conducting snapshot operations includes a snapshot management module that manages snapshot sets and a snapshot execution module that executes snapshot operations defined within the snapshot sets. In one embodiment, snapshot execution modules from each controller involved in the snapshot set are marshalled to conduct the snapshot operations specified within a snapshot set.  
         [0017]     The various elements of the present invention may be combined into a system for managing and conducting snapshot operations that includes a plurality of storage volumes configured to store data and one or more storage controllers configured to manage the storage volumes, add snapshot criteria to a snapshot set, and initiate a plurality of fast replications operations as specified by the snapshot set.  
         [0018]     The various elements and aspects of the present invention facilitate managing and conducting multiple snapshot operations as an atomic operation. The present invention reduces the programming burden associated with conducting snapshot operations and is particularly useful for archiving data distributed across multiple volumes such as data related to database applications and the like. These and other features and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     In order that the manner in which the advantages of the invention are obtained will be readily understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:  
         [0020]      FIG. 1  is a block diagram illustrating a network system representative of an environment wherein the present invention may be deployed;  
         [0021]      FIG. 2  is a block diagram illustrating a storage subsystem representative of an environment wherein the present invention may be deployed;  
         [0022]      FIG. 3  is a block diagram illustrating one embodiment of a snapshot management system of the present invention;  
         [0023]      FIG. 4  is a flow chart illustrating a snapshot management method of the present invention;  
         [0024]      FIG. 5  is a text-based diagram illustrating a snapshot management programming interface of the present invention; and  
         [0025]      FIG. 6  is a block diagram illustrating a snapshot criteria data structure in accordance with the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]     Many of the functional units described in this specification have been labeled as modules, in order to more particularly emphasize their implementation independence. For example, modules may be implemented in software for execution by various types of processors. An identified module of executable code may, for instance, comprise one or more physical or logical blocks of computer instructions which may, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified module need not be physically located together, but may comprise disparate instructions stored in different locations which, when joined logically together, comprise the module and achieve the stated purpose for the module. For example, a module of executable code could be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices.  
         [0027]     Modules may also be implemented in hardware as electronic circuits comprising custom VLSI circuitry, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A module may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices or the like.  
         [0028]     Similarly, operational data may be identified and illustrated herein within modules, and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different storage devices, and may exist, at least partially, merely as electronic signals on a system or network.  
         [0029]      FIG. 1  is a block diagram illustrating a network system  100  representative of an environment in which the present invention may be deployed. The depicted network system  100  includes a plurality of workstations  110  and servers  120  interconnected via a network  130 . The network  100  may comprise any type of network including a local area network and/or a wide area network.  
         [0030]     The depicted network system  100  also includes one or more storage subsystems  140  interconnected with the servers  120  via a storage network  150 . In one embodiment, the servers  120  are mainframe computers configured to conduct high bandwidth I/O operations with the storage subsystems  140 . In the depicted embodiment, the storage subsystems  140  are fault tolerant subsystems containing redundant storage controllers  160  and storage devices  170 .  
         [0031]      FIG. 2  is a schematic block diagram of a storage subsystem  200  illustrating the need for the present invention. The storage subsystem  200  is a representative example of subsystems in which the present invention may be deployed and is one example of the storage subsystem  140  depicted in  FIG. 1 . The storage subsystem  200  includes a storage array  210  and one or more controllers  220 . The storage subsystem  200  may include a plurality of controllers  220  that achieve increased reliability through redundancy. Additionally, the storage array  210  may also achieve increased reliability by interconnecting multiple storage devices  230  via an array loop  240 .  
         [0032]     In the depicted embodiment, the storage devices  230  are interconnected with an array loop  240 . The array loop  240  also interconnects the controllers  220  with the storage array  210 . The array loop  240  circulates communications in both directions to increase reliability and throughput. In one embodiment, the array loop  240  is a point-to-point loop such as those defined by the fibre channel standard.  
         [0033]     In the depicted embodiment, the controllers  220  each support a host connection  250 . The controllers  220  receive access requests via the host connection  250  and service those requests by transferring blocks of data to and from the storage array  210 . The blocks of data that are transferred to the storage array  210  may be redundantly encoded to permit error detection and data recovery in the event of failure of one of the storage devices  230 . Typically, the controllers  220  organize the storage devices  230  in a redundant manner and present one or more volumes for use by one or more servers or hosts such as those depicted in  FIG. 1 .  
         [0034]     In addition to connection and data redundancy, the controllers  220  may support various types of fast replication operations. Fast replication operations provide the appearance of an instant copy between a source volume and a target volume within a storage subsystem such as the storage subsystem  200 . Fast replication operations conduct data transfers from the source volume to the target volume at the convenience of the storage subsystem  200  without halting access to the source or target volumes by an external device, such as a host or server.  
         [0035]     The present invention reduces the complexity of conducting fast replication operations and their associated background copies and is particularly useful when conducting snapshot or other fast replication operations on data distributed across multiple volumes such as data associated with database applications and the like.  
         [0036]      FIG. 3  is a block diagram illustrating one embodiment of a snapshot management system  300  of the present invention. The depicted snapshot management system  300  includes a snapshot management module  310 , a snapshot execution module  320 , a metadata buffer  330 , and in selected embodiments, a snapshot programming interface  340 . The snapshot management system  300  manages snapshot operations and may be contained on selected controllers, or on each controller within a storage subsystem such as the storage subsystem  140 . In the depicted embodiment the snapshot management module  310 , the snapshot execution module  320 , and the metadata buffer  330  are located in a controller  220 , and the snapshot inferface module  340  is located in a server  120 .  
         [0037]     The snapshot management module  310  receives commands related to defining and conducting snapshot operations. The metadata buffer  330  contains metadata related to storage-based operations including data related to snapshot or fast replication operations. As depicted, snapshot definitions in the form of specific snapshot criteria are received, aggregated, and stored as one or more snapshot sets  332  within the metadata buffer  330 .  
         [0038]     Each snapshot set  332  may specify criteria for one or more fast replication operations that are seen as an atomic operation from the viewpoint of an application, system utility, or the like. Multiple volumes may be referenced within each snapshot set  332  in order to conduct snapshot operations on data distributed across multiple volumes. Examples of snapshot criteria contained within the snapshot set  332  will be discussed in greater detail in conjunction with  FIG. 6 .  
         [0039]     In one embodiment, the snapshot management module  310  receives commands from a snapshot interface module  340  residing on a host that provides a programming interface to an application, system utility, or the like. In the aforementioned embodiment, the commands received from the snapshot interface module correspond to function calls provided by the snapshot interface module  340  that may be invoked by an application, system utility, or the like. One example of a set of function calls suitable for use by the snapshot interface module  340  will be described subsequently in conjunction with  FIG. 5 .  
         [0040]     The snapshot execution module  320  executes fast replication (i.e. snapshot) operations defined by the snapshot criteria within each snapshot set. Multiple snapshot execution modules  320  located on different controllers may be marshalled to conduct the specified snapshot operations. In addition, some searching may be conducted by the snapshot management module  320  to find the target volumes, controllers, and snapshot execution modules  320  best suited to fulfill the snapshot criteria specified within each snapshot set.  
         [0041]      FIG. 4  is a flow chart illustrating a snapshot management method  400  of the present invention. The snapshot management method  400  may be conducted by the snapshot management module  310  contained within a storage controller  220  such those depicted in  FIG. 3 . The snapshot management method  400  may be used to manage and conduct snapshot operations via the snapshot sets aggregated within the metadata buffer  330 .  
         [0042]     As depicted, the snapshot management method  400  executes a variety of procedures related to managing and conducting snapshot operations. In response to reception of a snapshot command at step  405 , the precise command is ascertained via a variety of command tests, and a corresponding procedure is executed.  
         [0043]     The depicted command tests, include a create test  410 , a delete test  420 , an add criteria test  430 , a remove criteria test  440 , a get set test  450 , an initiate snapshot test  460 , a terminate shapshot test  470 , and a shutdown test  480 . The procedures associated with the depicted tests include, respectively, a create set procedure  415 , a delete set procedure  425 , an add criteria procedure  435 , a remove criteria procedure  445 , a provide information procedure  455 , an initiate snapshot procedure  465 , a terminate shapshot procedure  475 , and an initiate shutdown procedure  485 .  
         [0044]     The create set procedure  415  creates a snapshot set. In one embodiment, the created snapshot set is an empty list with a unique worldwide identification number (WWN) referred to as a snapshot setID. The setID facilitates distinguishing snapshot sets created on different controllers within a storage sub-system, storage network, wide-area network, or the like. The created snapshot set may be stored within a dedicated dataspace such as the metadata buffer  330  depicted in  FIG. 3 .  
         [0045]     The empty list created by the create set procedure  415  functions as a placeholder for subsequently specified snapshot criteria. In another embodiment, snapshot criteria or references to snapshot criteria may be sent along with the command associated with the create set procedure  415  and included within the created snapshot set.  
         [0046]     In contrast to the create set procedure  415 , the delete set procedure  425  deletes a snapshot set along with the specified snapshot criteria. In order to avoid generating duplicate setIDs, the setID may be retained on the originating controller.  
         [0047]     The add criteria procedure  435  adds specified snapshot criteria to a snapshot set. Likewise the remove criteria procedure  445  removes specified snapshot criteria from a snapshot set. In one embodiment, the snapshot criteria are specified via a data structure containing a plurality of data fields described in conjunction with  FIG. 6 .  
         [0048]     The provide information procedure  455  provides information pertaining to a specified snapshot set to a requestor. The provided information may include a list of WWNs of other controllers involved in the specified snapshot set. In one embodiment, a snapshot set maybe specified using a setID or by using first, last, previous, and next designators to iterate through the snapshot sets contained within a controller.  
         [0049]     The initiate snapshot procedure  465  initiates the snapshot operations within a snapshot set appearing, logically, as an atomic snapshot operation. The terminate snapshot procedure  475  terminates initiated snapshot operations while the initiate shutdown procedure  485  initiates a shutdown process and terminates the snapshot management method  400 .  
         [0050]     The snapshot management method  400  facilitates managing and conducting snapshot operations on data that may be distributed across multiple volumes. While the snapshot management method  400  is depicted as an execution loop with a separate test for each procedure that may be executed, a variety of invocation mechanisms known to those skilled in the art may used to execute the various procedures or steps included in the method  400 . Examples include an index driven procedure table common to code libraries and the like, and a set of event driven interrupts where each procedure is associated with a unique (software) interrupt.  
         [0051]     The depicted method  400  may be deployed within selected controllers or within every controller within a storage subsystem, storage network, wide-area network or the like. In one embodiment, the controllers involved with each snapshot set are included within the snapshot set and each involved controller is given a complete copy of the snapshot set. In the aforementioned embodiment, a command corresponding to the initiate snapshot procedure  465  may be sent to any controller having a copy of the snapshot set resulting in initiation of the fast replication operations specified in the snapshot set. In one embodiment, the command may be transmitted from any server  120  in a system  100 .  
         [0052]     Referring to  FIG. 5 , a snapshot management programming interface  500  provides a programming interface (API), for example on a host, for invoking the procedures of the snapshot management method  400 . The depicted interface  500  is one example of the snapshot interface  340  depicted in  FIG. 3 . The programming interface  500  simplifies the complexity of invoking the functionality provided by the snapshot management method  400 .  
         [0053]     As depicted, the programming interface  500  includes a plurality of functions for generating and managing a snapshot set. In one embodiment, the functions include, by way of example, a Create Snapshot Set function  515  and a Delete Snapshot Set function  525  corresponding to the create set procedure  415  and the delete set procedure  425 . The functions  515  and  525  facilitate creating and deleting snapshot sets. The depicted programming interface  500  also includes by way of example, an Add to Snapshot Set function  535  and a Remove From Snapshot Set function  545  corresponding to the add criteria procedure  435  and the remove criteria procedure  445 . The functions  535  and  545  facilitate adding and removing criteria to a snapshot set.  
         [0054]     The depicted programming interface  500  also includes in this example a Get Snapshot Set function  555  corresponding to the provide information procedure  455 , an Execute Snapshot Set function  565  corresponding to the initiate snapshot procedure  465 , and a Terminate Snapshot Set function  575  corresponding to the terminate snapshot procedure  475 . The function  555  provides information regarding a specified snapshot set, while the functions  565  and  575  facilitate initiating and terminating snapshot operations defined by a specified snapshot set.  
         [0055]     Referring to  FIG. 6 , a snapshot criteria data structure  600  includes a variety of data fields useful for defining snapshot operations that are to be conducted with the present invention. The depicted data structure  100  is one example of snapshot criteria that may be contained within the snapshot set  332  depicted in  FIG. 3 . The depicted data fields specify the nature of a fast replication operation that is to be included within a snapshot set and thereby provide a mechanism for conducting multiple fast replication operations as an atomic process from the vantage point of an application, system utility, or the like.  
         [0056]     As depicted the snapshot criteria data structure  600  includes a background copy indicator  610 , a partial volume indicator  620 , a source volume indicator  622 , a source extents indicator  624 , a redundancy indicator  630 , an autoselect target indicator  632 , a target volume indicator  634 , and a target extents indicator  636 .  
         [0057]     The background copy indicator  610  indicates whether the data transfers related to the snapshot operations are to be conducted as a background operation or deferred until the data to be transferred is about to be overwritten on the source volume. The partial volume indicator  620  indicates whether the entire volume is to be snapshot or a partial volume is to be snapshot as indicated by the source extents indicator  624 . The source volume indicator  622  indicates the volume to be snapshot while the source extents indicator  624  indicates the starting and ending indices of the regions (such as blocks, sectors or tracks) to be snapshot.  
         [0058]     The redundancy indicator  630  indicates the level of redundancy required for the target volume. In one embodiment, the redundancy levels range from JBOD (no redundancy) to to RAID level  50 . The auto-select target indicator  632  indicates whether the target volume is to be automatically selected or manually specified via the target volume indicator  634  and the target extents indicator  636 . The target volume indicator  634  indicates the target volume for the included snapshot operation while the target extents indicator  636  indicates the starting and ending indices of the regions to be used on the target volume.  
         [0059]     The present invention facilitates conducting multiple snapshot operations as an atomic operation and simplifies the complexity of managing those operations. Snapshot criteria are used to specify the fast replications operations involved in the atomic snapshot operation. Criteria may be specified without requiring a precise knowledge of the available target volumes.  
         [0060]     The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.