System and method for emulating block appended checksums on storage devices by sector stealing

• US 6,976,146 B1
• Filed: 05/21/2002
• Issued: 12/13/2005
• Est. Priority Date: 05/21/2002
• Status: Active Grant

• Current Assignee: Network Appliance Incorporated (NetApp, Inc.)
• Original Assignee: Network Appliance Incorporated (NetApp, Inc.)
• Inventors: Son, Kyquang, Lloyd, John, Aiello, Anthony F.
• Primary Examiner(s): Padmanabhan, Mano
• Assistant Examiner(s): Namazi, Mehdi
• Application Number:
  US10/152,448
• Time in Patent Office: 1,302 Days
• Field of Search: 711/153, 711/202, 711/114, 714/6
• US Class Current: 711/202
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 2211/1009 Cache, i.e. caches used in RAID system with parity

Abstract

A system and method for emulating conventional block appended checksums on storage devices that generally do not support such checksums in a block is provided. A grouping of data sectors with one or more checksum sectors is generated. This grouping is mapped to/from a file system data structure associated with a traditional block appended checksum disk drive.

Claims

1. A method for a computer to emulate block appended checksums on a storage device, the method comprising the steps of:

grouping a set of data sectors on the storage device with one or more checksum sectors, the one or more checksum sectors storing a checksum of data stored in the set of data sectors;

mapping, in response to a read operation of the storage device by the computer, the grouping of data sectors and checksum sectors to a file system data structure, wherein the read operation is performed as a single operation; and

mapping, in response to a write operation, a file system data structure to the set of data sectors and checksum sectors, wherein the write operation is performed as a single operation.

2. The method of claim 1 wherein the computer further comprises a file server.

3. The method of claim 1 wherein the set of data sectors further comprises eight data sectors.

4. The method of claim 1 wherein the one or more checksum sectors further comprises one checksum sector.

5. The method of claim 4 wherein the one or more checksum sectors further comprises 64 bytes of checksum information.

6. The method of claim 1 wherein the data sectors and checksum sectors are contiguous on the storage device.

7. The method of claim 1 wherein the one or more checksum sectors are written to any available location on the storage device.

8. The method of claim 1 wherein the data sectors and checksum sectors further comprise sectors having a size smaller than 520 bytes per sector.

9. The method of claim 8 wherein the data sectors and checksum sectors further comprise sectors having a size of 512 bytes per sector.

10. A computer for use with a storage device emulating block appended checksums, the computer comprising:

means for forming a grouping of a set of data sectors of the storage device with a set of checksum sectors; and

means for performing input/output operations with respect to the storage device by the computer utilizing the grouping of data sectors and checksum sectors so that the input/output operations are each performed on both the data sectors and checksums sectors in a single operation.

11. The computer of claim 10 wherein the data sectors and checksum sectors further comprise sectors having a size smaller than 520 bytes per sector.

12. The computer of claim 11 wherein the data sectors and checksum sectors further comprise sectors having a size of 512 bytes per sector.

13. The computer of claim 11 wherein the set of data sectors further comprises eight data sectors.

14. The computer of claim 10 wherein the set of checksum sectors further comprises one checksum sector.

15. A method for a computer to emulate block appended checksums on a storage device, the storage device being free of support for conventional block appended checksums, the method comprising the steps of:

forming a group comprising of a set of data sectors and one or more checksum sectors, the one or more checksum sectors storing a checksum of data stored in the set of data sectors; and

performing an input/output operation to the storage device utilizing the grouping so that the input/output operation is performed on both the data sectors and the one or more checksum sectors in a single operation.

16. The method of claim 15 wherein the computer further comprises a file server.

17. The method of claim 15 wherein the set of data sectors further comprises eight data sectors.

18. The method of claim 15 wherein the set of checksum sectors further comprises one checksum sector.

19. The method of claim 18 wherein the checksum sector further comprises 64 bytes of checksum information.

20. The method of claim 15 wherein the data sectors and checksum sectors are contiguous on the storage device.

21. The method of claim 15 wherein the one or more checksum sectors are written to any available location on the storage device.

22. The method of claim 15 wherein the data sectors and checksum sectors further comprise sectors having a size smaller than 520 bytes per sector.

23. The method of claim 15 wherein the data sectors and checksum sectors further comprise sectors having a size of 512 bytes per sector.

24. A computer-readable media, including program instructions executing on a computer, for emulating block appended checksums on a storage device, the computer-readable media including program instructions for performing the steps of:

grouping a set of data sectors on the storage device with a set of checksum sectors;

mapping, in response to a read operation of the storage device by the computer, the grouping of data sectors and checksum sectors to a file system data structure; and

mapping, in response to a write operation to the storage device by the computer, a file system data structure to this set of data sectors and checksum sectors.

25. A method for emulating block appended checksums on a disk having a set sector size for use with a file system having a set data size, the method comprising the steps of:

forming a group of sectors, the group of sectors comprising a number of sectors sufficient to store the set data size and an associated checksum;

mapping the data sectors and the checksum sectors to a file system data structure; and

performing input/output operations to the disk, wherein data written to the disk is mapped from the set of data structure to the group of sectors and wherein data retrieved from the disk is mapped from the group of sectors to the data structure.

26. The method of claim 25 wherein the set sector size further comprises 512 bytes per sector;

and

wherein a conventional block appended checksum requires a sector having a size of 520 bytes per sector.

27. The method of claim 25 wherein the set sector size further comprises 512 bytes per sector.

28. The method of claim 25 wherein the set data size further comprises 4,096 bytes.

29. A method for a computer to emulate block appended checksums using one or more 512 bytes per sector disks, the method comprising the steps of:

forming a group comprising of a set of data sectors and one or more checksum sectors, the one or more checksum sectors storing a checksum of data stored in the set of data sectors; and

performing an input/output operation to the one or more 512 bytes per sector disks utilizing the grouping so that the input/output operation is performed on both the data sectors and the one or more checksum sectors in a single operation.

30. A method for a computer to emulate a disk using block appended checksums having a first size of bytes per sectors using a disk having a second size bytes per sector, the method comprising the steps of:

forming a group of sectors of the disk having the second size bytes per sector comprising of a set of data sectors and one or more checksum sectors, the one or more checksum sectors storing a checksum of data stored in the set of data sectors; and

performing an input/output operation to the disk having the second size bytes per sector utilizing the grouping so that the input/output operation is performed on both the data sectors and the one or more checksum sectors in a single operation.

31. The method of claim 30 wherein the one or more checksum sectors may be stored at any location on the disk having the second size bytes per sector.

32. A computer, comprising:

a storage device having a plurality of blocks to store one of either data or checksums; and

a storage device driver to group a set of data blocks with one or more checksum blocks, the one or more checksum blocks storing a checksum of data stored in the set of data blocks, the group of data and checksum blocks arranged to permit input/output operations to be performed on the group of data and checksum blocks in a single operation.

33. The computer of claim 32 further comprising:

a disk as the storage device, the disk drive having a plurality of sectors as the plurality of blocks.

34. The computer of claim 32 further comprising:

read/write operations as the input/output operations.

35. The computer of claim 32 further comprising:

a file server as the computer.

36. The computer of claim 32 further comprising:

eight data blocks for the set of data blocks.

37. The computer of claim 32 further comprising:

one checksum block.

38. The computer of claim 32 further comprising:

a single checksum computed for the data stored in the set of data blocks.

39. The computer of claim 37 further comprising:

64 bytes of checksum information.

40. The computer of claim 32 further comprising:

a contiguous grouping of data blocks and checksum blocks on the storage device.

41. The computer of claim 32 further comprising:

the one or more checksum blocks are written to any available location on the storage device.

42. The computer of claim 32 further comprising:

data blocks and checksum blocks having a size smaller than 520 bytes per block.

43. The computer of claim 32 further comprising:

data blocks and checksum blocks having a size of 512 bytes per block.

44. A method for storing data and checksums on a storage device, the method comprising the steps of:

receiving N blocks of data at the storage device;

computing at least one checksum for the N blocks of data; and

storing the data in N blocks and the at least one checksum in an N+1 block, the N+1 blocks being logically grouped so that input/output operations may be performed on all N+1 blocks in one operation on the storage device.

45. The method of claim 44 further comprising:

using a disk as the storage device, the disk drive having a plurality of sectors as the plurality of blocks.

46. The method of claim 44 further comprising:

using read/write operations as the input/output operations.

47. The method of claim 44, further comprising:

storing eight blocks of data; and

storing the at least one checksum in a ninth block.

48. The method of claim 44, further comprising:

using blocks that contain 512 bytes.

49. The method of claim 44 further comprising:

computing a single checksum for the N blocks of data.

50. The method of claim 44, further comprising:

computing a checksum that contains 64 bytes of checksum information.

51. The method of claim 44, further comprising:

storing the N+1 blocks contiguously on the storage device.

52. A storage device for storing data and checksums, comprising:

a storage operating system to receive N blocks of data;

a processor to compute at least one checksum for the N blocks of data; and

a checksum module to store the data in N blocks and the at least one checksum in an N+1 block, the N+1 blocks being logically grouped so that input/output operations may be performed on all N+1 blocks in one operation on the storage device.

53. The storage device of claim 52 further comprising:

a sector as each of the plurality of blocks.

54. The storage device of claim 52 further comprising:

read/write operations as the input/output operations.

55. The storage device of claim 52, further comprising:

N+1 blocks that contain eight blocks of data and the at least one checksum in a ninth block.

56. The storage device of claim 52, further comprising:

512-byte blocks.

57. The storage device of claim 52 further comprising:

a single checksum computed for the N blocks of data.

58. The storage device of claim 52, further comprising:

64-byte checksums.

59. The storage device of claim 52, further comprising:

a contiguous grouping of the N+1 blocks on the storage device.

60. A storage device for storing data and checksums, comprising:

means for receiving N blocks of data at the storage device;

means for computing at least one checksum for the N blocks of data; and

means for storing the data in N blocks and the at least one checksum in an N+1 block, the N+1 blocks being logically grouped so that input/output operations may be performed on all N+1 blocks in one operation on the storage device.

61. A computer readable media, comprising:

the computer readable media containing instructions for execution on a processor for the practice of the method of,

receiving N blocks of data;

computing at least one checksum for the N blocks of data; and

storing the data in N blocks and the at least one checksum in an N+1 block, the N+1 blocks being logically grouped so that input/output operations may be performed on all N+1 blocks in one operation.