Verification of computer backup data

• US 20070186127A1
• Filed: 02/03/2006
• Published: 08/09/2007
• Est. Priority Date: 02/03/2006
• Status: Active Grant

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Desai, Asit, Boggis, Antony
• Granted Patent: US 8,015,441 B2
• Time in Patent Office: Days
• US Class Current: 714/13
• CPC Class Codes: G06F 11/1448 Management of the data involved in backup or backup restore
• CPC Class Codes: G06F 11/1464 for networked environments

Abstract

A backup method for a computer system network avoids generating hashes from data that may be inaccurate due to network errors affords verification of source data written to backup media includes reading at a network client a portion of the source data from a source storage volume and generating a hash of the source data at the client. The source data and hash are transmitted to a backup server and written to the backup media. The hash is written to the backup media is associated with the backup data corresponding to the source data from which the hash was generated. Verification of the backup data is performed by reading the backup data from the backup media, generating a hash from the backup data read, and comparing that hash with the hash originally stored on the backup media. This enables the backup data to be verified as corresponding to the original source data without the necessity of rereading the source data from the source volume, and enables faster, more accurate off-line verification subsequent to the backup process.

Claims

1. A method of backing up source data from a source storage volume of a source computer to backup media, comprising:

reading at least a portion of the source data from the source storage volume;

generating by the source computer a hash of the source data read from the source volume;

transmitting the source data and hash to said backup media;

writing the source data to said backup media as backup data;

writing the hash to the backup media; and

associating the hash with the backup data corresponding to the source data from which the hash was generated.

2. The method of claim 1, wherein said transmitting comprises transmitting the source data and hash to a backup server, and said writing of source data and hash to said backup media comprises writing by said backup server.

3. The method of claim 2, wherein said source computer and backup server are connected by a computer network comprising a plurality of interconnected source computers, each having one or more associated source volumes, and wherein each source computer transmits a portion of source data read from an associated source volume and a hash generated by such source computer from said read source data over said network to said backup server for writing on said backup media.

4. The method of claim 3 further comprising reading backup data and an associated hash from the backup media;

generating a second hash from the backup data read from the backup media; and

comparing the associated hash read from the backup media with the second hash to verify the integrity of the backup data.

5. The method of claim 4 further comprising, upon said compared hashes not matching, marking the backup data as miscomparing, rereading by a source computer the source data corresponding to the miscompared backup data media from the associated source volume, and rewriting the source data to the backup media with a new hash generated from the reread source data by the source computer.

6. The method of claim 5 further comprising generating by the source computer of the associated source volume another hash of the reread source data, and transmitting said other hash to the backup media for association with backup data corresponding to said reread source data.

7. The method of claim 6, wherein said associating said hash comprises writing a hash on the backup media for each block as part of such block.

8. The method of claim 1, wherein said portion of source data comprises a data file having one or more blocks of data, and said generating comprises generating a hash for each of said blocks.

9. The method of claim 8, wherein each of said blocks of data comprises a plurality of file data records, and wherein said generating comprises generating a hash for each of said records, and accumulating such hashes to produce a hash for the block.

10. A method of backing up source data from a source storage volume of a source computer over a network to backup media controlled by a backup server on said network, the source data being stored on said backup media as backup data with an associated hash of said source data generated by said source computer, comprising:

reading the backup data and its associated hash from the backup media;

generating another hash from the backup data read from the backup media; and

comparing the associated hash read from the backup media with said other hash to verify the integrity of the source data.

11. The method of claim 10 further comprising, upon said compared hashes not matching, marking the source data as miscomparing to indicate that the source data is to be rewritten from the source volume to the backup media.

12. The method of claim 10 further comprising reading the backup data and its associated hash from the backup media, and copying the backup data and the hash to another backup media.

19. The computer readable media of claim 12, wherein said computer system comprises a computer network, and said method is performed on a computer of said computer network.

13. Computer readable media comprising instructions executed by a source computer and a backup computer of a computer network to perform a backup method to backup source data stored on a source storage volume of said network, the method comprising:

reading by said source computer at least a portion of source data from the source storage volume;

generating by the source computer a hash of the source data read from the source volume;

transmitting by the source computer the source data and the hash to said backup server; and

writing by the backup server the source data and the hash to backup media.

14. The computer readable media of claim 13, wherein the method further comprises reading the backup data and its associated hash from the backup media;

generating another hash from the backup data read from the backup media; and

comparing the associated hash read from the backup media with said other hash to verify the integrity of the source data corresponding to the backup data from which the associated hash was generated.

15. The computer readable media of claim 14, wherein the method further comprises, upon said compared hashes not matching, marking the backup data as not comparing to indicate that the source data corresponding to the backup data is to be rewritten to the backup media upon performing a subsequent backup.

16. The computer readable media of claim 13, wherein said portion of source data comprises a data file including a block containing one or more file data records, each having a predetermined length, and wherein said generating comprises generating a hash for each of said data records and accumulating said hashes to produce a hash representing said data file.

17. The computer readable media of claim 16, wherein said associating of the hash with the backup data comprises writing said hash on the backup media for each data file as part of said block.

18. The computer readable media of claim 13, wherein the method further comprises reading metadata associated with said source data;

comparing the metadata with metadata in a catalog representing a backup of said source data on the backup media; and

the rewriting of the source data to the backup media upon said comparing of metadata indicating that the source data has changed.