Generation and use of a time map for accessing a prior image of a storage device

• US 20060047999A1
• Filed: 08/24/2004
• Published: 03/02/2006
• Est. Priority Date: 08/24/2004
• Status: Active Grant

• Current Assignee: Veritas Technologies, LLC (Whitehouse Group Ltd.)
• Original Assignee: Symantec Operating Corporation (NortonLifeLock Inc.)
• Inventors: Passerini, Ron, Zhang, Tianming
• Granted Patent: US 7,296,008 B2
• Time in Patent Office: Days
• US Class Current: 714/6
• CPC Class Codes: G06F 11/1458 Management of the backup or restore process
• CPC Class Codes: G06F 11/1461 Backup scheduling policy
• CPC Class Codes: G06F 11/1464 for networked environments
• CPC Class Codes: Y10S 707/99931 Database or file accessing
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

The invention relates to systems, methods, and articles of manufacture for generating an image of a data store at a past time by using a map (e.g., a time map) of the locations of data stored in the data store at the specified past time. The map allows the data storage system to quickly determine the locations of data stored in a data store at a past time, without searching the entire index of records concerning the locations of the past data.

Claims

1. A data storage system capable of presenting an image of a data store at a past time, the system comprising:

a receiver for receiving a specification for a past time;

an I/O processor which processes I/O requests directed to one or more target units of storage in a data store;

an indexing module which records write requests processed by the I/O processor, the indexing module comprising a memory storing, for each write request, a record comprising;

i) identification of target units of storage;

ii) locations of data previously stored in the target units of storage; and

iii) a write time denoting a time at which a write request was received;

a mapping module that uses one or more records to generate a map of the locations of data stored in the target units of storage at the specified past time; and

an image generation module that presents an image of the data store at the past time based, at least in part, on the map generated by the mapping module.

2. The data storage system of claim 1 wherein the image is also based on data currently stored in units of storage that have not been a target of a write request since the past time.

3. The data storage system of claim 1 wherein an additional entry is used by the mapping module when a newly-received write request is processed by the I/O processor.

4. The data storage system of claim 1 wherein the data store is a virtual data store.

5. The data storage system of claim 4 wherein the locations are locations in a physical store.

6. The data storage system of claim 1, wherein locations of data previously stored in the target units of storage can be located anywhere within the data storage system.

7. A method of generating a time map of a data store for a past time, the method comprising the steps of:

creating a record of write requests directed to one or more target units of storage located in a data store, each record comprising;

i) an identification of at least one target unit of storage;

ii) a write time denoting a time at which a write request directed to the at least one target unit of storage was received; and

iii) a location to which data stored in the at least one target unit of storage was moved in response to the write request; and

for a first past time, generating a time map of the data store at a generation time, by using the records to locate a current location of data for units of storage that were a target of a write request since the first past time.

8. The method of claim 7, further comprising the step of:

selecting, for each unit of storage, a record that is oldest among a set of records created since the first past time.

9. The method of claim 7, further comprising the step of:

after the generation time, supplementing the time map with additional records, in response to write requests directed to units of storage that had not previously been a target of a write request since the first past time.

10. The method of claim 7, further comprising the step of:

for a second past time, generating a time map of the data store by using records for units of storage that were a target of a write request since the second past time.

11. The method of claim 10, further comprising the step of:

using the time map for the first past time to create a first logical unit.

12. The method of claim 11, further comprising the step of:

using the time map for the second past time to a create a second logical unit.

13. The method of claim 12 wherein the first logical unit and the second logical unit are virtual logical units.

14. A method of generating an image of a data store at a past time, the method comprising the steps of:

processing I/O requests directed to a plurality of target units of storage in a data store;

recording an identification of the target units of storage, a location of data previously stored in the target units of storage, and a time, in response to one or more I/O requests;

mapping an association between the target units of storage and the current locations of data previously stored in the target units of storage at a past time; and

for the past time, generating an image of the data store based, at least in part, on the mapped associations.

15. The method of claim 14 wherein the method is implemented by a storage system, and the data previously stored in the target units of storage can be located anywhere within the storage system.

16. The method of claim 15 wherein the storage system comprises a storage management device and a physical store.

17. The method of claim 16 wherein the physical store comprises a plurality of logical units.

18. The method of claim 14 wherein the image is also based on data currently stored in target units of storage if an I/O request has not been directed to the units of storage since the past time.

19. The method of claim 14 wherein the mapping step further comprising:

in response to I/O requests received after the map is first generated, continuing to record identifications of the target units of storage, locations of data previously stored in the target units of storage, and times; and

mapping an additional association when a unit of storage not originally included in the map is the target of an I/O request.

20. The method of claim 14 wherein the I/O request is a write request.

21. The method of claim 14 wherein the time is the time at which the I/O request directed to the target unit of storage was received.

22. The method of claim 14 wherein a current image of the data store and the time image of the data store exist concurrently.