US20100070474A1 - Transferring or migrating portions of data objects, such as block-level data migration or chunk-based data migration - Google Patents

Abstract

A system and method for migrating data objects based on portions of the data objects is described. The system may transfer portions of files, folders, and other data objects from primary storage to secondary storage based on certain criteria, such as time-based criteria, age-based criteria, and so on. An increment may be one or more blocks of a data object, or one or more chunks of a data object, or other segments that combine to form or store a data object. For example, the system identifies one or more blocks of a data object that satisfy a certain criteria, and migrates the identified blocks. The system may determine that a certain number of blocks of a file have not been modified or called by a file system in a certain time period, and migrate these blocks to secondary storage.

Description

CROSS REFERENCE TO RELATED APPLICATIONS
• This application claims priority to U.S. Patent Application No. 61/096,587, filed on Sep. 12, 2008, entitled TRANSFERRING OR MIGRATING PORTIONS OF DATA OBJECTS, SUCH AS BLOCK-LEVEL DATA MIGRATION OR CHUNK-BASED DATA MIGRATION, which is incorporated by reference in its entirety.
BACKGROUND
• Data storage systems contain large amounts of data. This data includes personal data, such as financial data, customer/client/patient contact data, audio/visual data, and much more. Computer systems often contain word processing documents, engineering diagrams, spreadsheets, business strategy presentations, email mailboxes, and so on. With the proliferation of computer systems and the ease of creating content, the amount of content in an organization has expanded rapidly. Even small offices often have more information stored than any single employee can know about or locate.
• To that end, both companies and individuals rely on data storage systems to store, protect, and/or hold old data, such as data no longer actively needed. Often, these data storage systems perform data migration, moving data from primary storage (containing actively needed data) to secondary storage (such as backup storage or archives). Typical data storage systems transfer data in the forms of files, folders, and so on. For example, the typical data storage system may transfer data from a data store associated with a user to secondary storage while maintaining the structure and application format of the files themselves.
• To restore the data, these systems then require knowledge of applications that create the data. Additionally, some files, can be very large, and restoring a large file can be costly, time consuming, and resource intensive.
• The need exists for a system that overcomes the above problems, as well as one that provides additional benefits. Overall, the examples herein of some prior or related systems and their associated limitations are intended to be illustrative and not exclusive. Other limitations of existing or prior systems will become apparent to those of skill in the art upon reading the following Detailed Description.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a block diagram illustrating components of a data stream utilized by a suitable data storage system.
• FIG. 2 is a block diagram illustrating an example of a data storage system.
• FIG. 3 is a block diagram illustrating an example of components of a server used in data storage operations.
• FIG. 4 is a block diagram illustrating a system for performing increment-based data migration.
• FIG. 5 is a block diagram illustrating the intermediate component ofFIG. 4.
• FIGS. 6A and 6B are schematic diagrams illustrating a data store before and after a block-based data migration, respectively.
• FIG. 7 is a flow diagram illustrating a routine for performing block-level data migration.
• FIG. 8 is a block diagram illustrating a system for providing chunk-based data migration and/or restoration.
• FIG. 9 is a flow diagram illustrating a routine for performing chunk-level data migration.
• FIG. 10 is flow diagram illustrating a routine for block-based or chunk-based data restoration and modification.
DETAILED DESCRIPTIONOverview
• Described in detail herein is a system and method that transfers or migrates data objects (such as files, folders, data stores, and/or discrete data component(s) by migrating segments, portions, increments, or proper subsets of the data objects. The system may transfer increments of files, folders, and other data objects from primary storage (or other sources) to secondary storage based on certain criteria, such as time-based criteria, age-based criteria, and so on. An increment may be one or more blocks of a data object, or one or more chunks of a data object, or other portions that combine to form, store, and/or contain a data object, such as a file.
• In some examples, the system performs block-based migration of data. That is, the system identifies one or more blocks of a data object that satisfy a certain criteria, and migrates the identified blocks. For example, the system may determine that a certain number of blocks of a file have not been modified or called by a file system within a certain time period, and migrate these blocks to secondary storage. The system then maintains the other blocks of the file in primary storage. In some cases, the system automatically migrates data without requiring user input. Additionally, the migration may be transparent to a user.
• In some examples, the system performs chunk-based migration of data. A chunk is, for example, a group or set of blocks. One or more chunks may comprise a file, folder, or other data object. The system identifies one or more chunks of a data object that satisfy a certain criteria, and migrates the identified chunks. For example, the system may determine that a certain number of chunks of a file have not been modified or called by a file system in a certain time period, and migrate these chunks to secondary storage. The system then maintains the other chunks of the file in primary storage. Further details regarding chunks and chunk-based storage may be found in U.S. Patent Application No. 61/180,791, entitled BLOCK-LEVEL SINGLE INSTANCING, filed May 22, 2009.
• In some examples, the system leverages the block-based or chunk-based data migration in order to restore portions of data objects without restoring entire data objects. For example, the system can restore one or more blocks of a file, present the data contained by the blocks, receive modifications to the data, and update the blocks, and hence the file.
• The system will now be described with respect to various examples. The following description provides specific details for a thorough understanding of, and enabling description for, these examples of the system. However, one skilled in the art will understand that the system may be practiced without these details. In other instances, well-known structures and functions have not been shown or described in detail to avoid unnecessarily obscuring the description of the examples of the system.
• The terminology used in the description presented below is intended to be interpreted in its broadest reasonable manner, even though it is being used in conjunction with a detailed description of certain specific examples of the system. Certain terms may even be emphasized below; however, any terminology intended to be interpreted in any restricted manner will be overtly and specifically defined as such in this Detailed Description section.
Suitable System
• Referring toFIG. 1, a block diagram illustrating components of a data stream utilized by a suitable data storage and recovery system, such as a system that performs block-based and/or chunk-based data migration, is shown. Thestream110 may include aclient111, amedia agent112, and asecondary storage device113. For example, in storage operations, the system may store, receive and/or prepare data, such as blocks or chunks, to be stored, copied or backed up at a server orclient111. The system may then transfer the data to be stored tomedia agent112, which may then refer to storage policies, schedule policies, and/retention policies (and other policies) to choose asecondary storage device113. Themedia agent112 may include or be associated with an intermediate component, to be discussed herein.
• Thesecondary storage device113 receives the data from themedia agent112 and stores the data as a secondary copy, such as a backup copy. Secondary storage devices may be magnetic tapes, optical disks, USB and other similar media, disk and tape drives, and so on. Of course, the system may employ other configurations of stream components not shown in the Figure.
• Referring toFIG. 2, a block diagram illustrating an example of a data storage andrecovery system200 is shown. Data storage systems may contain some or all of the following components, depending on the needs of the system.FIG. 2 and the following discussion provide a brief, general description of a suitable computing environment in which the system can be implemented. Although not required, aspects of the system are described in the general context of computer-executable instructions, such as routines executed by a general-purpose computer, e.g., a server computer, wireless device or personal computer. Those skilled in the relevant art will appreciate that the system can be practiced with other communications, data processing, or computer system configurations, including: Internet appliances, network PCs, mini-computers, mainframe computers, and the like. Indeed, the terms “computer,” “host,” and “host computer” are generally used interchangeably herein, and refer to any of the above devices and systems, as well as any data processor.
• Aspects of the system can be embodied in a special purpose computer or data processor that is specifically programmed, configured, or constructed to perform one or more of the computer-executable instructions explained in detail herein. Aspects of the system can also be practiced in distributed computing environments where tasks or modules are performed by remote processing devices, which are linked through a communications network, such as a Local Area Network (LAN), Wide Area Network (WAN), Storage Area Network (SAN), Fibre Channel, or the Internet. In a distributed computing environment, program modules may be located in both local and remote memory storage devices.
• Aspects of the system may be stored or distributed on computer-readable media, including tangible storage media, such as magnetically or optically readable computer discs, hard-wired or preprogrammed chips (e.g., EEPROM semiconductor chips), nanotechnology memory, biological memory, or other data storage media. Indeed, computer implemented instructions, data structures, screen displays, and other data under aspects of the system may be distributed over the Internet or over other networks (including wireless networks), on a propagated signal on a propagation medium (e.g., an electromagnetic wave(s), a sound wave, etc.) over a period of time, or they may be provided on any analog or digital network (packet switched, circuit switched, or other scheme). Those skilled in the relevant art will recognize that portions of the system reside on a server computer, while corresponding portions reside on a client computer, and thus, while certain hardware platforms are described herein, aspects of the system are equally applicable to nodes on a network.
• For example, thedata storage system200 contains astorage manager210, one ormore clients111, one ormore media agents112, and one ormore storage devices113.Storage manager210controls media agents112, which may be responsible for transferring data tostorage devices113.Storage manager210 includes ajobs agent211, amanagement agent212, adatabase213, and/or aninterface module214.Storage manager210 communicates with client(s)111. One ormore clients111 may access data to be stored by the system fromdatabase222 via adata agent221. The system usesmedia agents112, which containdatabases231, to transfer and store data intostorage devices113.Client databases222 may contain data files and other information, while media agent databases may contain indices and other data structures that store the data at secondary storage devices, for example.
• The data storage and recovery system may include software and/or hardware components and modules used in data storage operations. The components may be storage resources that function to copy data during storage operations. The components may perform other storage operations (or storage management operations) other that operations used in data stores. For example, some resources may create, store, retrieve, and/or migrate primary or secondary data copies of data. Additionally, some resources may create indices and other tables relied upon by the data storage system and other data recovery systems. The secondary copies may include snapshot copies and associated indices, but may also include other backup copies such as HSM copies, archive copies, auxiliary copies, and so on. The resources may also perform storage management functions that may communicate information to higher level components, such as global management resources.
• In some examples, the system performs storage operations based on storage policies, as mentioned above. For example, a storage policy includes a set of preferences or other criteria to be considered during storage operations. The storage policy may determine or define a storage location and/or set of preferences about how the system transfers data to the location and what processes the system performs on the data before, during, or after the data transfer. In some cases, a storage policy may define a logical bucket in which to transfer, store or copy data from a source to a data store, such as storage media. Storage policies may be stored instorage manager210, or may be stored in other resources, such as a global manager, a media agent, and so on. Further details regarding storage management and resources for storage management will now be discussed.
• Referring toFIG. 3, a block diagram illustrating an example of components of a server used in data storage operations is shown. A server, such asstorage manager210, may communicate withclients111 to determine data to be copied to storage media. As described above, thestorage manager210 may contain ajobs agent211, amanagement agent212, adatabase213, and/or an interface module.Jobs agent211 may manage and control the scheduling of jobs (such as copying data files) fromclients111 tomedia agents112.Management agent212 may control the overall functionality and processes of the data storage system, or may communicate with global managers.Database213 or another data structure may store storage policies, schedule policies, retention policies, or other information, such as historical storage statistics, storage trend statistics, and so on. Interface module215 may interact with a user interface, enabling the system to present information to administrators and receive feedback or other input from the administrators or with other components of the system (such as via APIs).
• In some examples, the system performs some or all the operations described herein using an intermediate component, virtual storage device, virtual device driver, virtual disk driver, or other intermediary capable of mounting to a file system and communicating with a storage device. That is, an intermediate component may communicatively reside between a file system and a primary data store that contains data created by the file system and a secondary data store. The intermediate component enables flexibility during data restoration, enabling a file system to indirectly access a secondary copy of data in order to identify information associated with data stored by the secondary copy, among other benefits.
Data Migration System
• Referring toFIG. 4, a block diagram illustrating a system for performing portion-based data migration is shown. The system components include a data creation and/ormodification component410, anintermediate component420, and adata storage component430. The restorecomponent410 may include aclient portion415, such as a client portion that receives input from users. Afile system417, as discussed herein, may organize and provide data to applications, user interfaces, and so on to the user, among other things. The file system creates, updates, modifies, and/or removes data from a data store, based on input from users. Thefile system417 may store the created data in one or more data stores, such as alocal database418 that provides primary storage. For example, thedatabase418 may be a hard drive or hard disk that stores data produced by the file system as primary copies or production copies of the data. The system components may also include an intermediate component420 (further described herein), such as a virtual disk driver. Theintermediate component420 communicates with adisk driver435 and mounteddisk437, which together may act as thedata storage component430. Additionally, theintermediate component420 may be located between thefile system417 anddatabase418. The data storage component provides secondary storage, and may store secondary copies of data generated by thefile system417, such as secondary copies of primary copies stored indatabase418.
• Referring toFIG. 5, a block diagram illustrating theintermediate component420 ofFIG. 4 is shown. Theintermediate component420 includes a restoremodule510 that may contain itsown file system515. The restore module510 (or component, sub-system, and so on), may communicate with a file system, such as thefile system417. Further details with respect the functionality of the restoremodule510 is described herein.
• Theintermediate component420 may also include astorage device module520 that communicates with storage devices, such asdisk driver435 and disk437 (or other fixed or removable media). Thestorage device module520 may include anindex525 or allocation table that identifies available media for data storage, contains information associated with data stored via theintermediate component420, and so on.
• Theintermediate component420 may also include a cache530 (or, a cache module or interface that communicates with an external cache), and/or other agents ormodules540, such as modules that index files, classify files, manage files or information, and so on.
Block-Based Data Migration
• Block-level migration, or block-based data migration, involves migrating disk blocks from a primary data store (e.g., a disk partition) to secondary media. Using block-level migration, a data storage system transfers blocks on a disk partition that have not been recently accessed to secondary storage, freeing up space on the disk. In order to expand the database, the system moves data from the database to other locations, such as other databases or storage locations. Typically, such expansion requires knowledge of the database, such as the database application, the database schema, and so on. However, using block-level migration, the system can expand or extend a database without any knowledge of the applications or schema of the database, providing for transparent migration and/or restoration of data from one storage location to another. This can be helpful when migrating data from virtual machines that contain large files, (e.g., large files created by applications such as Vmware, Microsoft Virtual Server, and so on). The system may implement block-level migration processes as software device drivers, but may also implement block-level migration in disk hardware.
• As described herein, the system can transfer or migrate certain blocks of a data object from one data store to another, such as from primary storage that contains a primary copy of the data object to secondary storage that contains or will contain a secondary copy of the primary copy of the data object. Referring toFIGS. 6A-6B, a schematic diagram illustrating contents of two data stores before and after a block-based data migration is shown. InFIG. 6A, afirst data store610 contains primary copies (i.e., production copies) of two data objects, afirst data object620 and asecond data object630. The first data object comprises blocks A and A¹, where blocks A are blocks that satisfy or meet certain storage criteria (such as blocks that have not been modified since creation or not been modified within a certain period of time) and blocks A′ are blocks that do not meet the criteria (such as blocks that have been modified within the certain time period). The second data object comprises blocks B and B′, where blocks B satisfy the criteria and blocks B′ do not meet the criteria.
• FIG. 6B depicts thefirst data store610 after a block-based data migration of the twodata objects620 and630. In this example, the system only transfers the data from blocks that satisfy a criteria (blocks A and B) from thefirst data store610 to asecond data store640, such assecondary storage642,644. The secondary storage may include one or more magnetic tapes, one or more optical disks, and so on. The system maintains data in the remaining blocks (blocks A′ and B′) within thefirst data store610.
• The system can perform file system data migration at a block level, unlike previous systems that only migrate data at the file level (that is, they have a file-level granularity). By tracking migrated blocks, the system can also restore data at the block level, which may avoid cost and time problems associated with restoring data at the file level or may assist in defragmenting a storage device. Further details regarding the block-level restoration of data is be discussed herein.
• Referring toFIG. 7, a flow diagram illustrating a routine700 for performing block-level data migration is shown. Instep710, the system identifies data blocks within a data store that satisfy a certain criteria. The system may track data blocks and access the blocks via APIs. The data store may be a database associated with a file system, a SQL database, a Microsoft Exchange mailbox, and so on. The system may compare some or all of the blocks (or, information associated with the blocks) of the data store with predetermined criteria. The predetermined criteria may be time-based criteria within a storage policy or data retention policy.
• In some examples, the system identifies blocks set to be “aged off” from the data store. That is, the system identifies blocks created, changed, or last modified before a certain date and time. For example, the system may review a data store for all data blocks that satisfy a criterion or criteria. The data store may be an electronic mailbox or personal folders (.pst) file for a Microsoft Exchange user, and the criterion may define, for example, all blocks or emails last modified or changed thirty days ago or earlier. The system compares information associated with the blocks, such as metadata associated with the blocks, to the criteria, and identifies all blocks that satisfy the criteria. For example, the system identifies all blocks in the .pst file not modified within the past thirty days. The identified blocks may include all the blocks for some emails and/or a portion of the blocks for other emails. That is, for a given email (or data object), a first portion of the blocks that include the email may satisfy the criteria, while a second portion of the blocks that include the same email may not satisfy the criteria. In other words, a file or a data object can be divided into parts or portions, and only some of the parts or portions change.
• To determine which blocks have changed, and when, the system can monitor the activity of the file system via theintermediate component420, (e.g., the virtual device driver). The system may store a data structure, such as a bitmap, table, log, and so on within thecache530 or other memory of theintermediate component420, and update the bitmap whenever the file system calls thedatabase418 to access and update or change data blocks within thedatabase418. Theintermediate component420 traps the command to the disk driver, where that command identifies certain blocks on a disk for access or modifications, and writes to the bitmap the changed blocks and the time of the change. The bitmap may include information such as an identification of changed blocks and a date and a time the blocks were changed. The bitmap, which may be a table, data structure, or group of pointers, such as a snapshot, may also include other information, such as information that maps file names to blocks, information that maps chunks to blocks and/or file names, and so on. Table 1 provides entry information for a bitmap tracking the activity of a file system with the “/users” directory:

• 	TABLE 1
  	Blocks	Date and Time Modified
  	/users/blocks1-100	09.08.2008 @14:30
  	/users/blocks101-105	09.04.2008 @12:23
  	/users2/blocks106-110	09.04.2008 @11:34
  	/users3/blocks110-1000	08.05.2008 @10:34

• Thus, if a storage policy identified the time 08.30.2008 @ 12:00 as a threshold time criteria, where data modified after the time is to be retained, the system would identify, instep710, blocks110-1000 as having satisfied the criteria. Thus, the system, via theintermediate component420, can monitor what blocks are requested by a file system, and act accordingly, as described herein.
• Instep720, the system transfers data within the identified blocks from the data store to a media agent, to be stored in a different data store. The system may perform some or all of the processes described with respect toFIGS. 1-3 when transferring the data to the media agent. For example, before transferring data, the system may review a storage policy as described herein to select a media agent, such asmedia agent112, based on instructions within the storage policy. Instep725, the system optionally updates an allocation table, such as a file allocation table (FAT) for a file system associated with the data store, to indicate the data blocks that no longer contain data and are now free to receive and store data from the file system.
• Instep730, via the media agent, the system stores data from the blocks to a different data store. In some cases, the system, via the media agent, stores the data from the blocks to a secondary storage device, such as a magnetic tape or optical disk. For example, the system may store the data from the blocks in secondary copies of the data store, such as a backup copy, an archive copy, and so on. In some cases, the system stores the data from the blocks to a storage device located near and/or associated with the data store, such as to a quick recovery volume that facilitates quick restores of data.
• The system may create, generate, update, and/or include an allocation table, (such as a table for the data store) that tracks the transferred data and the data that was not transferred. The table may include information identifying the original data blocks for the data, the name of the data object, the location of any transferred data blocks, and so on. For example, Table 2 provides entry information for an example .pst file:

• 	TABLE 2
  	Name of Data Object	Location of data
  	Email1	C:/users/blocks1-100
  	Email2.1 (body of email)	C:/users/blocks101-120
  	Email2.2 (attachment)	X:/remov1/blocks1-250
  	Email3	X:/remov2/blocks300-500

• In the above example, the data for “Email2” is stored in two locations, a local data store (C:/) and an off-site data store (X:/). The system maintains the body of the email, recently modified or accessed, at a location within a data store associated with a file system, “C:/users/blocks101-120.” The system stores the attachment, not recently modified or accessed, in a separate data store, “X:/remov1/blocks1-250.” Of course, the table may include other information, fields, or entries not shown. For example, when the system stored data to tape, the table may include tape identification information, tape offset information, and so on.
Chunk-Based Data Migration
• Chunked file migration, or chunk-based data migration, involves splitting a data object into two or more portions of the data object, creating an index that tracks the portions, and storing the data object to secondary storage via the two or more portions. Among other things, the chunk-based migration provides for fast and efficient storage of a data object. Additionally, chunk-based migration facilitates fast and efficient recall of a data object, such as the large files described herein. For example, if a user modifies a migrated file, chunk-based migration enables a data restore component to only retrieve from, and migrate back to, secondary storage the chunk containing the modified portion of the file, and not the entire file. In some cases, chunk-based migration may collaborate with components that provide file format and/or database schema information in order to facilitate data recovery.
• As described above, in some examples the system migrates chunks of data (sets of blocks) that comprise a data object from one data store to another. Referring toFIG. 8, a block diagram illustrating asystem800 for providing chunk-based data migration and/or restoration is shown. Thesystem800 includes afile system810, acallback layer820, which interacts with the file system, and adevice driver830, which reads from and writes data to adata store840 such as removable media including magnetic tapes, optical disks, and so on. Further details with respect to thecallback layer820 will be described herein.
• As described above, the system migrates data via one or more chunks, such as sets of blocks. A data object, such as a file, may comprise two or more chunks. A chunk may be a logical division of a data object. For example, a .pst file may include two or more chucks: a first chunk that stores data associated with an index of a user's mailbox, and one or more chunks that stores email, attachments, and so on within the user's mailbox. A chunk is a proper subset of all the blocks comprising a file. That is, for a file consisting of n blocks, the largest chunk of the file comprises at most n−1 blocks.
• Thesystem800 may include achunking component815 that divides data objects, such as files, into chunks. Thechunking component815 may receive files to be stored indatabase418, divide the files into two or more chunks, and store the files as two or more chunks indatabase418. Thechunking component815 may update an index that associated information associated with files with the chunks of the file, the data blocks of the chunks, and so on.
• Thechunking component815 may perform different processes when determining how to divide a data object. For example, thechunking component815 may include indexing, header, and other identifying information or metadata in a first chunk, and include the payload in other chunks. Thechunking component815 may follow a rules-based process when dividing a data object. The rules may define a minimum or maximum data size for a chunk, a time of creation for data within a chunk, a type of data within a chunk, and so on.
• For example, thechunking component815 may divide a user mailbox (such as a .pst file) into a number of chunks, based on various rules that assign emails within the mailbox to chunks based on the metadata associated with the emails. Thechunking component815 may place an index of the mailbox in a first chunk and the emails in other chunks. Thechunking component815 may then divide the other chunks based on dates of creation, deletion or reception of the emails, size of the emails, sender of the emails, type of emails, and so on. Thus, as an example, the chunking component may divide a mailbox as follows:

• 	User1/Chunk1	Index
  	User1/Chunk2	Sent emails
  	User1/Chunk3	Received emails
  	User1/Chunk4	Deleted emails
  	User1/Chunk5	All Attachments.

  
  Of course, other divisions are possible. Chunks may not necessarily fall within logical divisions. For example, the chunking component may divide a data object based on information or instructions not associated with the data object, such as information about data storage resources, information about a target secondary storage device, historical information about previous divisions, and so on.
• The system may perform chunking at various times or in different locations of a data storage system. For example, althoughFIG. 8 shows thechunking component815 atfile system810, the system may locate the chunking component at thedevice driver830, at an intermediate component, or other locations. In some cases, the system may utilize thechunking component815 to divide data already in secondary storage into chunks. For example, a data storage system may retrieve data objects under management that were transferred to secondary storage using file-based data migration, divide the data objects into two or more chunks, and migrate the data objects based to storage using the chunk-based data migration discussed herein. Thus, future restoration of the data objects may be faster and easier because the data objects are divided into chunks.
• Referring toFIG. 9, a flow diagram illustrating a routine900 for performing chunk-level data migration is shown. Instep910, the system identifies chunks of data blocks within a data store that satisfy one or more criteria. The data store may store large files (>50 MB), such as databases associated with a file system, SQL databases, Microsoft Exchange mailboxes, virtual machine files, and so on. The system may compare some or all of the chunks (or, information associated with the chunks) of the data store with predetermined and/or dynamic criteria. The predetermined criteria may be time-based criteria within a storage policy or data retention policy. The system may review an index with thechunking component815 when comparing the chunks with applicable criteria.
• Instep920, the system transfers data within the identified chunks from the data store to a media agent, to be stored in a different data store. The system may perform some or all of the processes described with respect toFIGS. 1-3 when transferring the data to the media agent. For example, the system may review a storage policy assigned to the data store and select a media agent based on instructions within the storage policy. Instep925, the system optionally updates an allocation table, such as a file allocation table (FAT) for a file system associated with the data store, to indicate the data blocks that no longer contain data and are now free to receive and store data from the file system.
• In some examples, the system monitors the transfer of data from the file system to the data store via thecallback layer820. Thecallback layer820 may be a layer, or additional file system, that resides on top of thefile system810. Theintermediate layer820 may intercept data requests from thefile system810, in order to identify, track and/or monitor the chunks requested by thefile system810 and store information associated with these requests in a data structure, such as a bitmap similar to the one shown in Table 1. Thus, theintermediate layer820 stores information identifying when chunks are accessed by tracking calls from thefile system810 to thedata store840. For example, Table 3 provides entry information for a bitmap tracking calls to a data store:

• 	TABLE 3
  	Chunk of File1	Access Time
  	File1.1	09.05.2008 @12:00
  	File1.2	09.05.2008 @12:30
  	File1.3	09.05.2008 @13:30
  	File1.4	06.04.2008 @12:30

• In this example, thefile system810 creates a data object named “File1,” using the chunking component to divide the file into four chunks: “File1.1,” “File1.2,” “File1.3,” and “File1.4.” Thefile system810 stores the four chunks todata store840 on 06.04.2008. According to the table, the file system has not accessed File1.4 since its creation, and most recently accessed the other chunks on Sep. 5, 2008. Of course, Table 3 may include other or different information, such as information identifying a location of the chunks, information identifying the type of media storing the chunks, information identifying the blocks within the chunk, and/or other information or metadata.
• Instep930, via the media agent, the system stores the data from the chunks to a different data store. In some cases, the system, via the media agent, stores the data to a secondary storage device, such as a magnetic tape or optical disk. For example, the system may store the data in secondary copies of the data store, such as a backup copy, and archive copy, and so on. In some cases, the system stores the data to a storage device located near and/or associated with the data store, such as to a quick recovery volume.
Data Recovery
• The system, using the block-based or chunk-based data migration processes described herein, is able to restore portions of files instead of entire files, such as individual blocks or chunks that comprise portions of the files. Referring toFIG. 10, a flow diagram illustrating a routine1000 for block-based or chunk-based data restoration and modification is shown. Instep1010, the system, via a restore or data recovery component, receives a request to modify a file located in a data store. For example, a user submits a request to a file system to provide an old copy of a large Powerpoint presentation so the user can modify a picture located on slide5 of300 of the presentation. For example, thedata recovery component410 works with thefile system417 and thedata store430.
• Instep1020, the system identifies one or more blocks or one or more chunks associated with the request. For example, the system looks to a table similar to Table 2, and identifies blocks associated with page 5 of the presentation and blocks associated with an table of contents of the presentation.
• Instep1030, the system retrieves the identified blocks or chunks and presents them to the user. For example, the system only retrieves page 5 and table of contents of the presentation and presents the pages to the user.
• Instep1040, the system, via the file system, modifies the retrieved blocks or chunks via the file system. For example, the user updates the Powerpoint presentation to include a different picture. Instep1050, the system transfers data associated with the modified blocks or chunks to the data store. For example, the system transfers the modified page 5 to the data store. The system may also update a table that tracks access to the data store, such as Table 1 or Table 3.
• Thus, the system, leveraging block-based or chunk-based data migration during data storage, restores only portions of data objects required by a file system. Such restoration can be, among other benefits, advantageous over systems that perform file-based restoration, because those systems restore entire files, which can be expensive, time consuming, and so on. Some files, such as .pst files, may contain large amounts of data. File-based restoration can therefore be inconvenient and cumbersome, among other things, especially when a user only requires a small portion of a large file.
• For example, a user submits a request to the system to retrieve an old email stored in a secondary copy on removable media. The system identifies a portion of a .pst file associated with the user that contains a list of old emails, and retrieves the list. That is, the system has knowledge of the chunk that includes the list (e.g., a chunking component may always include the list in a first chunk of a data object), accesses the chunk, and retrieves the list. The other portions (e.g., all the emails with the .pst file), are not retrieved from media. The user selects the desired email from the list. The system, via an index that associates chunks with data (such as an index similar to Table 2), identifies the chunk that contains the email, and retrieves the chunk for presentation to the user. The index may include information about the chunks, information about the data objects (such as file formats, database schemas, application specific information, and so on).
• Thus, the system is able to restore the email without restoring the entire mailbox (.pst file) associated with the user. That is, although an entire data object is in storage, the system is able to retrieve a portion of the entire data object by leveraging the processes described herein.
CONCLUSION
• From the foregoing, it will be appreciated that specific examples of the data recovery system have been described herein for purposes of illustration, but that various modifications may be made without deviating from the spirit and scope of the system. For example, although files have been described, other types of content such as user settings, application data, emails, and other data objects can be imaged by snapshots. Accordingly, the system is not limited except as by the appended claims.
• Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise,” “comprising,” and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to.” The word “coupled”, as generally used herein, refers to two or more elements that may be either directly connected, or connected by way of one or more intermediate elements. Additionally, the words “herein,” “above,” “below,” and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application. Where the context permits, words in the above Detailed Description using the singular or plural number may also include the plural or singular number respectively. The word “or” in reference to a list of two or more items, that word covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list.
• The above detailed description of embodiments of the system is not intended to be exhaustive or to limit the system to the precise form disclosed above. While specific embodiments of, and examples for, the system are described above for illustrative purposes, various equivalent modifications are possible within the scope of the system, as those skilled in the relevant art will recognize. For example, while processes or blocks are presented in a given order, alternative embodiments may perform routines having steps, or employ systems having blocks, in a different order, and some processes or blocks may be deleted, moved, added, subdivided, combined, and/or modified. Each of these processes or blocks may be implemented in a variety of different ways. Also, while processes or blocks are at times shown as being performed in series, these processes or blocks may instead be performed in parallel, or may be performed at different times.
• The teachings of the system provided herein can be applied to other systems, not necessarily the system described above. The elements and acts of the various embodiments described above can be combined to provide further embodiments.
• These and other changes can be made to the system in light of the above Detailed Description. While the above description details certain embodiments of the system and describes the best mode contemplated, no matter how detailed the above appears in text, the system can be practiced in many ways. Details of the system may vary considerably in implementation details, while still being encompassed by the system disclosed herein. As noted above, particular terminology used when describing certain features or aspects of the system should not be taken to imply that the terminology is being redefined herein to be restricted to any specific characteristics, features, or aspects of the system with which that terminology is associated. In general, the terms used in the following claims should not be construed to limit the system to the specific embodiments disclosed in the specification, unless the above Detailed Description section explicitly defines such terms. Accordingly, the actual scope of the system encompasses not only the disclosed embodiments, but also all equivalent ways of practicing or implementing the system under the claims.
• While certain aspects of the system are presented below in certain claim forms, the applicant contemplates the various aspects of the system in any number of claim forms. For example, while only one aspect of the system is recited as a means-plus-function claim under 35 U.S.C sec. 112, sixth paragraph, other aspects may likewise be embodied as a means-plus-function claim, or in other forms, such as being embodied in a computer-readable medium. (Any claims intended to be treated under 35 U.S.C. §112, ¶6 will begin with the words “means for”.) Accordingly, the applicant reserves the right to add additional claims after filing the application to pursue such additional claim forms for other aspects of the system.

Claims (22)

1. A system for migrating data from a primary storage device to a secondary storage device, wherein the system includes a file system for transferring data to the primary storage device, and wherein the system further includes a disk driver for at least writing data received from the file system to the primary storage device and a secondary driver for at least writing data to the secondary storage device, the system comprising:

a virtual disk driver that receives data from the file system associated with the primary storage device and provides data to the disk driver that writes data to the primary storage device, wherein the virtual disk driver includes:

a data reception component, wherein the data reception component is configured to receive data from the file system, wherein the received data identifies multiple blocks of a file to be modified, wherein the multiple blocks are a proper subset of the total number of blocks for the file;

a data interception component, wherein the data interception component is configured to intercept the received data and extract information associated with the received data, wherein the extracted information includes information identifying the multiple blocks to be modified;

an index component, wherein the index component is configured to update an index that associates the extracted information with data blocks on the secondary storage device that contain the received data; and

a data transfer component, wherein the data transfer component is configured to transfer the received data to the secondary driver for storage to the secondary storage device;

a block-level data migration component, wherein the block-level migration component is configured to identify data blocks within the primary storage device that satisfy one or more predetermined criteria;

a data management component, configured to communicate with the virtual disk driver, the block-level data migration component and one or more media agents, wherein the data management component includes a storage policy that provides the one or more predetermined criteria, the storage policy identifying a time period in which to retain data within the primary storage device and identifying the one or more media agents in which to transfer the data from the file system to the disk driver, via the virtual disk driver; and

a media agent, wherein the media agent is one of the identified media agents and is configured to:

transfer data from the identified data blocks to the secondary driver; and

update an index that associates the transferred data with the secondary storage device that stores data from the secondary driver.

2. The system ofclaim 1, wherein the block-level data migration component is configured to identify data blocks that have not been accessed by the file system within a predetermined time period, and wherein the secondary storage device includes a magnetic tape drive.

3. The system ofclaim 1, wherein the block-level data migration component is configured to identify data blocks that have not changed after a predetermined time period, and wherein the multiple blocks are written to the secondary storage device in a format that is not native to a format for an application that created the file.

4. The system ofclaim 1, wherein the block-level data migration component further comprises:

an allocation table including one or more entries that associate data with data blocks that store the data, the one or more entries including:

first information that identifies data blocks that store the data; and

second information that identifies a date and time of a most recent access to the data blocks.

5. A method for storing a data object in two or more different data stores, the method comprising:

identifying data blocks representing a data object in a first data store, wherein the data object is a discrete data object managed by a file system;

for the identified data blocks:

identifying a portion of the identified data blocks that satisfies one or more data storage criteria, wherein the one or more data storage criteria is associated with a recent access of the identified data blocks;

and

transferring data stored by the portion of the identified data blocks that satisfies the one or more data storage criteria to a second data store, wherein the second data store is associated with data that satisfies the one or more data storage criteria.

6. The method ofclaim 5, further comprising:

updating an index associated with the data object to include information associating the portion of the identified data blocks with the second data store; and

removing information from an allocation table associated with the file system, wherein the removed information associates the transferred data with the first data store.

7. The method ofclaim 5, further comprising:

after transferring the data stored by the portion of the identified data blocks to the second data store:

identifying, from a portion of the identified data blocks that does not satisfy the one or more data storage criteria, one or more data blocks that satisfy the data retention criteria; and

transferring the identified one or more blocks to the second data store.

8. The method ofclaim 5, wherein the one or more data storage criteria includes a time period in which to retain data in the first data store.

9. The method ofclaim 5, wherein the one or more data storage criteria defines a time period in which the recent access must satisfy.

10. The method ofclaim 5, wherein the first data store includes a disk drive associated with the file system and the second data store includes removable media located in a different location than a location of the disk drive.

11. A tangible computer-readable storage medium whose contents cause a data storage system to perform a method of migrating data from primary storage to secondary storage, the method comprising:

identifying no more than n−1 data blocks, located within primary storage, that satisfy a criteria, wherein the n−1 data blocks represent a portion of a data file consisting of n blocks and the n blocks contain data written by a file system associated with the primary storage; and

transferring data contained by the identified no more than n−1 data blocks from the primary storage to the secondary storage.

12. The computer-readable medium ofclaim 11, further comprising:

updating a table to include information associating the transferred data with information identifying blocks within the secondary storage that contain the transferred data.

13. The computer-readable medium ofclaim 11, further comprising:

updating a table to include information associating the transferred data with information identifying tape offsets for the secondary storage that contain the transferred data.

14. The computer-readable medium ofclaim 11, further comprising:

removing information associated with the identified blocks from an allocation table of the file system.

15. The computer-readable medium ofclaim 11, wherein the criteria defines a time period in which the file system last accessed the blocks of the primary storage.

16. The computer-readable medium ofclaim 11, wherein the criteria defines a time period in which changes were made to data contained by the primary storage.

17. The computer-readable medium ofclaim 11, wherein the criteria defines a time period in which the data contained by the primary storage was created.

18. The computer-readable medium ofclaim 11, wherein primary storage includes a data file for a virtual machine.

19. A method in a data storage system for restoring a portion of a file, the method comprising:

receiving, at a file system, a request from a user to modify a portion of a file, wherein the file is at least partially stored in secondary storage on a storage device located at a location geographically different than a location for the file system;

identifying one or more data blocks within the storage device that contain data associated with the portion of the file to be modified;

retrieving the data contained by the identified one or more data blocks without retrieving all data blocks associated with the file;

presenting the retrieved data to the user; and

upon receiving input from the user to modify the portion of the file, transferring data associated with the received input for storage by the storage device.

20. A system for restoring a portion of a file, the system comprising:

means, at a file system, for receiving a request from a user to modify a portion of a file, wherein the file is at least partially stored in secondary storage on a storage device located at a location geographically different than a location for the file system;

means for identifying one or more data blocks within the storage device that contain data associated with the portion of the file to be modified;

means for retrieving the data contained by the identified one or more data blocks without retrieving all data blocks associated with the file;

means for presenting the retrieved data to the user; and

means for transferring data associated with the received input for storage by the storage device upon receiving input from the user to modify the portion of the file.

21. The system ofclaim 20, wherein the identified one or more data blocks are a proper subset of a set of data blocks that contain associated with the file.

22. The system ofclaim 20, wherein the means for identifying one or more data blocks identifies one or more chunks within the storage device.

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