Restore accelerator for serial media backup systems

• US 20070136540A1
• Filed: 12/08/2005
• Published: 06/14/2007
• Est. Priority Date: 12/08/2005
• Status: Active Grant

• Current Assignee: Quality Systems Associates, Inc.
• Original Assignee: Quality Systems Associates, Inc.
• Inventors: Matlock, Clarence
• Granted Patent: US 7,577,786 B2
• Time in Patent Office: Days
• US Class Current: 711/162
• CPC Class Codes: G06F 11/1451 by selection of backup contents
• CPC Class Codes: G06F 11/1469 Backup restoration techniques
• CPC Class Codes: G11B 2220/90 Tape-like record carriers
• CPC Class Codes: G11B 27/36 Monitoring, i.e. supervising the progress of recording or reproducing for digital recording G11B20/00 and s.gr.; for monitoring, testing or measuring of TV recorders of the type covered by H04N5/76 and subgroups, see H04N17/06
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99955 Archiving or backup

Abstract

A method for accelerating a tape backup system restore process receives a list of files that are to be restored and searches a tape catalogue to find tape volume and file sequence numbers for each file in the list of files, where the catalogue is an alphabetical listing of the contents of one or more backup tape volumes. The process appends the tape volume and file sequence numbers for each of the files to the list of files and then sorts the list of files according to tape volume and file sequence number. Accordingly, a list is obtained including the files that are to be restored, ordered according to the location of the files on the backup tape volumes. The restore process is accelerated by restoring files sequentially from this list and skipping over any intermediate files that are not on the list.

Claims

1. A method of retrieving desired backup data from a tape, the method comprising the steps of:

a) obtaining, from a client, a name of a desired file to be retrieved;

b) using the obtained name, obtaining a location on the tape of the desired file the location indicating a number of files on the tape to be skipped before the desired file;

c) retrieving the desired file according to its location in the tape by skipping the indicated number of files; and

d) passing the retrieved file to the restore process as the desired file.

2. A method according to claim 1, wherein step b) includes the step of obtaining a file index value indicating a number of files preceding the desired file on the tape and step c) includes the steps of:

c1) receiving the file index value;

c2) issuing an open command to a tape drive on which the tape is mounted;

c3) issuing a read command to the tape drive;

c4) obtaining a file header record from the tape drive in response to the read command;

c5) decrementing the file index value;

c6) issuing a forwarding command to the tape drive; and

c7) repeating steps c5)-c6) until the index value equals zero; and

p1 step d) includes the step of providing, to the restore process, the obtained file header record as the file header record of the desired file.

3. A method according to claim 2, wherein step d) further comprises the step of obtaining, from the tape drive, file data records corresponding to the file header record at the desired file header location and providing the file data records to the restore process.

4. A method according to claim 3, further comprising the step, prior to step d) of determining whether the file header record corresponds to the desired file.

5. The method of claim 4, wherein step d) includes the step of passing an error code to the restore process if the file header record does not correspond to the desired file.

6. A method according to claim 2, wherein step c4) further includes the steps of:

receiving a beginning of tape record from the tape drive in response to the read command; and

receiving one or more tape header records from the tape drive in response to the read command.

7. A method according to claim 2, further comprising the steps after step c) and before step d) of:

adjusting a sequence number in the file header record; and

calculating, for the file data records, a new checksum according to the adjusted sequence number.

8. A method according to claim 7, further comprising the steps of receiving an open tape drive command from the restore process prior to issuing the open tape command in step c2) and receiving a read tape drive command from the restore process prior to issuing the read command at step c3), the method further comprising the step of passing the beginning of tape record to the restore process after step c2) and passing the one or more tape header records to the restore process after step c3).

9. A method according to claim 8, further comprising the step of adjusting a sequence number of one or more of the beginning of tape record and the one or more tape header records before passing to the restore process.

10. A method according to claim 8, further comprising, during step d), the steps of:

d1) receiving an end of tape record from the tape drive in response to the read command;

d2) passing the end of tape record to the restore process;

d3) receiving one or more tape trailer records from the tape drive in response to the read command; and

d4) passing the one or more tape trailer records to the restore process.

11. A method according to claim 10, further comprising the step of adjusting a sequence number of one or more of the end of tape record and the one or more tape trailer records before passing the end of tape record and the one or more tape trailer records to the restore process.

12. A method of file retrieval from a backup tape set, the method comprising the steps of:

a) receiving an indication of one or more files that are to be retrieved;

b) determining a location of each of the one or more files on the backup tape set;

c) retrieving the one or more files according to their determined location on the backup tape set by skipping over any files in the tape set that are not to be retrieved.

13. A method according to claim 12, wherein the indication is a parameter string and step (a) includes receiving the parameter string from one of a command file or a command line and parsing the parameter string to obtain a list of the one or more files that are to be retrieved.

14. A method according to claim 12, wherein step b) includes the steps of:

b1) obtaining a list of files on the backup tape set from one of a media management product or a spooler listing;

b2) obtaining, from the list of files, a volume number and a file sequence number on the tape volume for each of the one or more files that are to be retrieved; and

b3) generating a sequence of the one or more files that are to be retrieved sorted by the respective volume and file sequence numbers of the files to be retrieved;

wherein and

step (c) includes the step of retrieving the one or more files according to the sequence.

15. A method according to claim 14, wherein step (c) includes:

c1) mounting a tape in the backup tape set containing a first file in the sequence on a tape drive;

c2) positioning to the tape on the tape drive to a first file in the sequence;

c3) forwarding, to a restore process, file data corresponding to the first file in the sequence; and

c4) repeating steps c2) and c3) for any remaining files in the sequence until the file data corresponding to a last file in the sequence is forwarded to the restore process.

16. A method according to claim 15, wherein step c3) adjusts a file sequence number of the first file and calculates a modified checksum of the first file prior to forwarding the file data to the restore process.

17. A method according to claim 15, wherein step c4) stops repeating for the one or more remaining files in the sequence if a tape trailer code is received prior to reaching the last file, the method further including the steps of:

f) halting the restore process;

g) starting a new restore process; and

h) repeating steps c1) through c4) for at least a first remaining file of the one or more remaining files in the sequence.

18. A method according to claim 15, wherein step c4) stops repeating for the one or more remaining files in the sequence if a tape trailer code is received prior to reaching the last file, the method further including the steps of:

f) adjusting one or more of a last file sequence number, a last filename, and a last file checksum value in the tape trailer code;

g) forwarding the tape trailer code to the restore process; and

h) repeating steps c1) through c4) for a next tape in the backup tape set, wherein the next tape contains at least a first remaining file of the one or more remaining files in the sequence.

19. A method according to claim 15, further including the step of receiving a file header code, wherein step (c2) skips any files that are not to be retrieved based on the file header code, and step (c3) also forwards, to the restore process, an adjusted file header code having a modified file sequence number and a modified checksum.

20. A system for restoring backup data from a sequential data storage medium, the system comprising a general purpose computer and computer software for controlling the general purpose computer, the software including:

a restore process for

receiving requests, from a client, for retrieval of backup data from the sequential data storage medium,

sending open and read commands to the data storage medium, receiving the backup data, and

providing the backup data to the client; and

a restore accelerator process for

intercepting the open and read commands sent from the restore process to the data storage medium,

gathering information about contents of the data storage medium and locations of the backup data that are to be retrieved,

sending new open and read commands to the data storage medium to sequentially position the sequential data storage medium to respective locations of the backup data that are to be retrieved,

retrieving the backup data from the data storage medium, while skipping intervening data that is not to be retrieved,

modifying one or more file sequence numbers and checksum values of the backup data, and

forwarding the backup data to the restore process.