Virtual storage and block level direct access of secondary storage for recovery of backup data

• US 6,269,431 B1
• Filed: 08/13/1998
• Issued: 07/31/2001
• Est. Priority Date: 08/13/1998
• Status: Expired due to Term

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Dunham, Scott R.
• Primary Examiner(s): Ellis, Richard L.
• Application Number:
  US09/133,564
• Time in Patent Office: 1,083 Days
• Field of Search: 711/2, 711/4, 711/6, 711/161, 711/162, 711/165, 707/2, 707/204, 707/205
• US Class Current: 711/162
• CPC Class Codes: G06F 11/1451 by selection of backup contents
• CPC Class Codes: G06F 11/1456 Hardware arrangements for backup
• CPC Class Codes: G06F 11/1458 Management of the backup or restore process
• CPC Class Codes: G06F 11/1469 Backup restoration techniques
• CPC Class Codes: G06F 11/2005 using redundant communication controllers
• CPC Class Codes: G06F 11/2007 using redundant communication media
• CPC Class Codes: G06F 11/2089 Redundant storage control functionality
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99955 Archiving or backup

Abstract

A data storage system has a primary data storage subsystem including primary data storage and a secondary data storage subsystem including secondary data storage. The secondary data storage contains backup versions of data stored in the primary data storage. To permit a host processor to access a specified backup version, the primary data storage subsystem assigns a virtual storage address to a specified backup version, and the host processor sends to the primary data storage subsystem data access requests that specify the virtual storage address. If the primary data storage subsystem has spare data storage, then a copy of the specified backup version is read from the secondary storage and written into the spare storage, and the address of the copy in the spare storage is mapped to the virtual storage address and accessed in response to the storage access requests from the host processor. Otherwise, a block-level direct access of the secondary storage is performed to access the specified backup version. In either case, the backup version appears to be in the primary data storage subsystem when the host accesses it.

Claims

1. A method of permitting at least one host processor to obtain from a data storage subsystem access to backup versions, the data storage subsystem having primary data storage, the backup versions being stored in secondary data storage linked to the data storage subsystem for transfer of the backup versions from the secondary data storage to the data storage subsystem, said method comprising:

a) the host processor transmitting to the data storage subsystem a request for assignment of a virtual storage address from which a specified backup version in the secondary data storage can be accessed via storage access requests that are transmitted from the host processor to the data storage subsystem;

b) the data storage subsystem responding to the request for assignment of a virtual storage address by assigning a virtual storage address from which the specified backup version in the secondary data storage can be accessed via storage access requests that are transmitted from the host processor to the data storage subsystem;

c) the host processor accessing the specified backup version by transmitting to the data storage subsystem storage access requests that specify the assigned virtual storage address and that specify portions of the specified backup version to be accessed; and

d) the data storage subsystem responding to the storage access requests by accessing the specified portions of the specified backup version to be accessed.

2. The method as claimed in claim 1, wherein the data storage subsystem further responds to the request for assignment of a virtual storage address by checking whether or not spare data storage is available in the data storage subsystem for storage of the specified backup version, and when spare data storage is available in the data storage subsystem for storage of the specified backup version, allocating the spare data storage for storage of the specified backup version, mapping the assigned virtual storage address to an address of the spare data storage allocated for storing the specified backup version, and transmitting a copy of the specified backup version from the secondary data storage to the spare data storage allocated for storing the specified backup version.

3. The method as claimed in claim 1, wherein the data storage subsystem responds to the data storage access requests by checking whether or not the specified virtual storage address is mapped to data storage in the data storage subsystem, and when the specified virtual storage address is found to be mapped to data storage in the data storage subsystem, accessing the data storage in the data storage subsystem to which the specified virtual storage address is found to be mapped.

4. The method as claimed in claim 1, wherein the secondary data storage includes tape storage and disk storage, and the specified backup version is stored in the tape storage, and wherein the data storage subsystem further responds to the request for assignment of a virtual storage address by checking whether or not spare data storage is available in the data storage subsystem for storage of the specified backup version, and when spare data storage is not available in the data storage subsystem for storage of the specified backup version, issuing a prefetch command to the secondary data storage for reading a copy of the specified backup version from the tape storage and storing the copy of the specified backup version in the disk storage.

5. The method as claimed in claim 1, wherein the data storage subsystem responds to the data storage access requests by checking whether or not the specified virtual storage address is mapped to data storage in the data storage subsystem, and when the specified virtual storage address is found not to be mapped to data storage in the data storage subsystem, transmitting storage access requests to the secondary data storage to access the specified backup version in the secondary data storage.

6. The method as claimed in claim 1, wherein the data storage subsystem responds to the data storage access requests by transmitting storage access requests to the secondary data storage to access the specified backup version in the secondary data storage.

7. The method as claimed in claim 1, wherein the specified backup version contains a logical data structure including a series of physical storage components, and wherein the method includes the host processor performing a logical-to-physical translation by identifying the physical storage components of the logical data structure in the specified backup version, and by transmitting the data storage access requests to the data storage subsystem for copying the physical storage components of the logical data structure from the specified backup version to create a current version of the logical data structure in the primary data storage of the data storage subsystem.

8. A machine-readable program storage device containing a program for a storage controller of a data storage subsystem permitting at least one host processor to obtain from the data storage subsystem access to backup versions, the backup versions being stored in secondary data storage linked to the data storage subsystem for transfer of the backup versions from the secondary data storage to the data storage subsystem, said program being executable by the storage controller for:

a) receiving from the host processor a request for assignment of a virtual storage address from which a specified backup version in the secondary data storage can be accessed via storage access requests that are transmitted from the host processor to the data storage subsystem;

b) responding to the request for assignment of a virtual storage address by assigning a virtual storage address from which the specified backup version in the secondary data storage can be accessed via storage access requests that are transmitted from the host processor to the data storage subsystem;

c) receiving from the host processor storage access requests that specify the assigned virtual storage address and that specify portions of the specified backup version to be accessed; and

d) responding to the data storage access requests by accessing the specified portions of the specified backup version to be accessed.

9. The machine readable program storage device as claimed in claim 8, wherein the program is executable by the data storage controller for responding to the request for assignment of a virtual storage address by checking whether or not spare data storage is available in the data storage subsystem for storage of the specified backup version, and when spare data storage is available in the data storage subsystem for storage of the specified backup version, allocating the spare data storage for storage of the specified backup version, mapping the assigned virtual storage address to an address of the spare data storage allocated for storing the specified backup version, and transmitting a copy of the specified backup version from the secondary data storage to the spare data storage allocated for storing the specified backup version.

10. The machine readable program storage device as claimed in claim 8, wherein the program is executable by the storage controller for responding to the storage access requests by checking whether or not the specified virtual storage address is mapped to data storage in the data storage subsystem, and when the specified virtual storage address is found to be mapped to data storage in the data storage subsystem, accessing the data storage in the data storage subsystem to which the specified virtual storage address is found to be mapped.

11. The machine readable program storage device as claimed in claim 8, wherein the secondary data storage includes disk storage and tape storage, the specified backup version is stored in the tape storage and the program is executable by the storage controller for responding to the request for assignment of a virtual storage address by checking whether or not spare data storage is available in the data storage subsystem for storage of the specified backup version, and when spare data storage is not available in the data storage subsystem for storage of the specified backup version, issuing a prefetch command to the secondary data storage for reading a copy of the specified backup version from the tape storage and writing the copy of the specified backup version to the disk storage.

12. The machine readable program storage device as claimed in claim 8, wherein the storage controller is programmed for responding to the storage access requests by checking whether or not the specified virtual storage address is mapped to data storage in the data storage subsystem, and when the specified virtual storage address is found not to be mapped to data storage in the data storage subsystem, transmitting storage access requests to the secondary data storage to access the specified backup version in the secondary data storage.

13. The machine readable program storage device as claimed in claim 8, wherein the storage controller is programmed for responding to the storage access requests by transmitting storage access requests to the secondary data storage to access the specified backup version in the secondary data storage.

14. A machine readable program storage device containing a program for a storage controller for a data storage subsystem permitting at least one host processor to obtain from the data storage subsystem access to backup versions, the backup versions being stored in secondary data storage linked to the data storage subsystem for transfer of the backup version from the secondary data storage to the data storage subsystem, said program being executable by the storage controller for:

a) receiving from the host processor a request for allocation of spare data storage from which a specified backup version can be accessed via storage access requests transmitted from the host processor to the data storage subsystem, and responding to the request from the host processor for allocation of the spare data storage by associating a virtual storage address with the specified backup version, and checking whether or not spare data storage is available in the data storage subsystem for storage of the specified backup version, and when spare data storage is available in the data storage subsystem for storage of the specified backup version, allocating the spare data storage for storing the specified backup version, mapping the virtual storage address to an address of the spare data storage allocated for storing the specified backup version, and transmitting a copy of the specified backup version from the secondary data storage to the spare data storage allocated for storing the specified backup version; and

b) receiving from the host processor storage access requests specifying said virtual storage address; and

responding to the storage access requests from the host processor by checking whether or not there is a mapping of the specified virtual storage address to data storage in the data storage subsystem, and when there is a mapping of the specified virtual storage address to data storage in the data storage subsystem, accessing the data storage in the data storage subsystem to which the virtual storage address is mapped, and when there is not a mapping of the specified virtual storage address to data storage in the data storage subsystem, then accessing the specified backup version associated with the virtual storage address by accessing the secondary data storage.

15. The machine readable program storage device as claimed in claim 14, wherein the secondary data storage includes disk storage and tape storage, and the specified backup version is stored in the tape storage, and the program is executable by the storage controller for responding to the request from the host processor for allocation of the spare data storage when spare data storage is not available in the data storage subsystem for storage of the specified backup version by transmitting a prefetch request from the data storage subsystem to the secondary data storage for reading a copy of the specified backup version from the tape storage, and writing the copy of the specified backup version to the disk storage.

16. A data storage subsystem for permitting at least one host processor to obtain access to backup versions stored in secondary data storage, wherein the data storage subsystem comprises primary data storage and a storage controller coupled to the primary data storage for controlling access to the primary data storage, the storage controller having at least one data port for linking the primary data storage and the secondary data storage to the host processor for transfer of data between the primary data storage and the secondary data storage and the host processor, wherein the storage controller is programmed for:

a) receiving from the host processor a request for assignment of a virtual storage address from which a specified backup version in the secondary data storage can be accessed via storage access requests that are transmitted from the host processor to the storage controller;

b) responding to the request for assignment of a virtual storage address by assigning a virtual storage address from which the specified backup version in the secondary data storage can be accessed via storage access requests that are transmitted from the host processor to the storage controller;

c) receiving from the host processor storage access requests that specify the assigned virtual storage address and that specify portions of the specified backup version to be accessed; and

d) responding to the storage access requests by accessing the specified portions of the specified backup version to be accessed.

17. The data storage subsystem as claimed in claim 16, wherein the program is executable by the storage controller for responding to the request for assignment of a virtual storage address by checking whether or not spare data storage is available in the data storage subsystem for storage of the specified backup version, and when spare data storage is available in the data storage subsystem for storage of the specified backup version, allocating the spare data storage for storage of the specified backup version, mapping the assigned virtual storage address to an address of the spare data storage allocated for storing the specified backup version, and transmitting a copy of the specified backup version from the secondary data storage to the spare data storage allocated for storing the specified backup version.

18. The data storage subsystem as claimed in claim 16, wherein the program is executable by the storage controller for responding to the storage access requests by checking whether or not the specified virtual storage address is mapped to data storage in the data storage subsystem, and when the specified virtual storage address is found to be mapped to data storage in the data storage subsystem, accessing the data storage in the data storage subsystem to which the specified virtual storage address is found to be mapped.

19. The data storage subsystem as claimed in claim 16, wherein the secondary data storage includes disk storage and tape storage, the specified backup version is stored in the tape storage, and the program is executable by the storage controller for responding to the request for assignment of a virtual storage address by checking whether or not spare data storage is available in the data storage subsystem for storage of the specified backup version, and when spare data storage is not available in the data storage subsystem for storage of the specified backup version, issuing a prefetch command to the secondary data storage for reading a copy of the specified backup version from the tape storage and writing the copy of the specified backup version to the disk storage.

20. The data storage subsystem as claimed in claim 16, wherein the storage controller is programmed for responding to the storage access requests by checking whether or not the specified virtual storage address is mapped to data storage in the data storage subsystem, and when the specified virtual storage address is found not to be mapped to data storage in the data storage subsystem, transmitting storage access requests to the secondary data storage to access the specified backup version in the secondary data storage.

21. The data storage subsystem as claimed in claim 16, wherein the storage controller is programmed for responding to the storage access requests by transmitting storage access requests to the secondary data storage to access the specified backup version in the secondary data storage.

22. A data storage subsystem for permitting at least one host processor to obtain access to backup versions stored in secondary data storage, wherein the data storage subsystem comprises primary data storage and a storage controller coupled to the primary data storage for controlling access to the primary data storage, the storage controller having at least one data port for linking the primary data storage and the secondary data storage to the host processor for transfer of data between the primary data storage and the secondary data storage and the host processor, wherein the storage controller is programmed for:

a) receiving from the host processor a request for allocation of spare data storage from which a specified backup version in the secondary data storage can be accessed via storage access requests transmitted from the host processor to the data storage subsystem, and responding to the request from the host processor for allocation of the spare data storage by associating a virtual storage address with the specified backup version, and checking whether or not spare data storage is available in the data storage subsystem for storage of the specified backup version, and when spare data storage is available in the data storage subsystem for storage of the specified backup version, allocating the spare data storage for storing the specified backup version, mapping the virtual storage address to an address of the spare data storage allocated for storing the specified backup version, and transmitting a copy of the specified backup version from the secondary data storage to the spare data storage allocated for storing the specified backup version; and

b) receiving from the host processor storage access requests specifying said virtual storage address; and

responding to the storage access requests from the host processor by checking whether or not there is a mapping of the specified virtual storage address to data storage in the data storage subsystem, and when there is a mapping of the specified virtual storage address to data storage in the data storage subsystem, accessing the data storage in the data storage subsystem to which the virtual storage address is mapped, and when there is not a mapping of the specified virtual storage address to data storage in the data storage subsystem, then accessing the specified backup version associated with the virtual storage address by accessing the secondary data storage.

23. The data storage subsystem as claimed in claim 22, wherein the secondary data storage includes disk storage and tape storage, the specified backup version is stored in the tape storage, and the program is executable by the storage controller for responding to the request from the host processor for allocation of the spare data storage when spare data storage is not available in the data storage subsystem for storage of the specified backup version by transmitting a prefetch request from the data storage subsystem to the secondary data storage for reading a copy of the specified backup version from the tape storage and writing the copy of the specified backup version to the disk storage.