Data backup method and system using snapshot and virtual tape

• US 6,625,704 B2
• Filed: 08/08/2001
• Issued: 09/23/2003
• Est. Priority Date: 08/08/2001
• Status: Expired due to Term

• Current Assignee: Hitachi Vantara, LLC (Hitachi, Ltd.)
• Original Assignee: Sepaton Incorporated (Hitachi, Ltd.)
• Inventors: Winokur, Alexander
• Primary Examiner(s): Thai, Tuan V.
• Application Number:
  US09/923,384
• Publication Number:
  US 20030037211A1
• Time in Patent Office: 776 Days
• Field of Search: 711/100, 711/112, 711/154, 711/162, 711/202
• US Class Current: 711/162
• 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 2201/84 Using snapshots, i.e. a logical point-in-time copy of the data

Abstract

A method of creating a snapshot copy of data stored on a first direct access storage device is described. It includes the acts of receiving information identifying a set of data that is to be copied from the first direct access storage device and mapping destination locations in a second direct access storage device for each element of the set. The destination locations are in a sequence emulating a tape copy. The method also includes the acts of iterating through the set of data. For the each element of the set, the method of the present invention also includes the acts of determining if the element has already been copied to the second direct access storage device, and, if the element has not already been copied, then copying the element to its mapped location in the second direct access storage device. A corresponding system is also described.

Claims

1. A method of creating a virtual tape image snapshot copy of data stored on a first direct access storage device, comprising the acts of:

(a) receiving information identifying a set of data that is to be copied from the first direct access storage device;

(b) mapping destination locations in a second direct access storage device for each element of the set, wherein the destination locations are in a sequence emulating a tape copy; and

(c) iterating through the set of data and for the each element of the set;

(c-1) determining if the element has already been copied to the second direct access storage device; and

(c-2) if the element has not already been copied, then copying the element to its mapped location in the second direct access storage device.

2. The method of claim 1 further comprising the act of:

during the iterating act, intercepting a write command to an element that has not yet been copied, wherein, if such a write command is intercepted, copying the element from the first direct access storage device to its mapped location in the second direct access storage device, then executing the write command.

3. The method of claim 1 further comprising the act of:

retrieving the set of data stored in the first direct access storage device using a first file access protocol.

4. The method of claim 3 wherein the first input-output (I/O) access protocol is Enterprise Systems Connection (ESCON) protocol.

5. The method of claim 1 further comprising the act of:

storing the set of data into the second direct access storage device using a second input-output (I/O) access protocol (SCSI/FC).

6. The method of claim 5 wherein the second file access protocol is Open System protocol.

7. The method of claim 1 further comprising the act of:

identifying the elements of the set of data; and

calculating computer memory size information of each of the elements in the first direct access storage device.

8. The method of claim 7 further comprising the act of:

creating an ordered list in order to extract the size information from the first direct access storage device, wherein each entry of the ordered list is associated with one of the elements of the set; and

storing into each entry physical block addresses of one or more memory blocks that store the element associated with the entry.

9. The method of claim 7 further comprising the act of:

creating an ordered list in order to extract the size information from the first direct access storage device, wherein each entry of the ordered list is associated with one of the elements of the set;

storing into each entry physical cylinder and head (CH) addresses of one or more tracks that store the element associated with the entry.

10. The method of claim 7 further comprising the acts of:

creating a file system size table, wherein each entry of the size table includes information relating to at least one of fields, key fields and data field for one or more records on one of a plurality of tracks; and

updating the file system size table each time a format write I/O command is administered to one of the plurality of tracks.

11. The method of claim 1 further comprising the act of:

calculating a computer memory size required in the second direct access storage device to copy each element of the set from the first direct access storage device.

12. The method of claim 1 further comprising the acts of:

creating a bit array, each bit of the bit array associated with one of the elements of the set; and

initializing each bit of the bit array to a first state, wherein the first state of each bit designates that the element associated therewith is not yet copied.

13. The method of claim 12 further comprising the act of:

changing the first state of one of bits in the bit array, when the element associated with the one of bits has been copied from the first direct access storage device to the second direct access storage device.

14. The method of claim 1 further comprising:

copying data stored on the snapshot copy directly on to a tape.

15. The method of claim 1, wherein the act (c) is performed in parallel with respect to the elements.

16. A system of creating a snapshot copy of data stored on a first direct access storage device, comprising:

(a) means for receiving information identifying a set of data that is to be copied from the first direct access storage device;

(b) means for mapping destination locations in a second direct access storage device for each element of the set, wherein the destination locations are in a sequence emulating a tape copy; and

(c) means for iterating through the set of data, comprising;

(c-1) means for determining if the each element of the set has already been copied to the second direct access storage device; and

(c-2) means for copying the element to its mapped location in the second direct access storage device if the element has not already been copied.

17. The system of claim 16 further comprising:

means for intercepting a write command to an element that has not yet been copied, wherein, if such a write command is intercepted, copying the element from the first direct access storage device to its mapped location in the second direct access storage device, then executing the write command.

18. The system of claim 16 further comprising:

means for retrieving the set of data stored in the first direct access storage device using a first file access protocol.

19. The system of claim 18 wherein the first file access protocol is Enterprise Systems Connection (ESCON) protocol.

20. The system of claim 16 further comprising:

means for storing the set of data into the second direct access storage device using a second input-output (I/O) protocol.

21. The system of claim 20 wherein the second file access protocol is Open System protocol.

22. The system of claim 16 further comprising:

means for identifying the elements of the set of data; and

means for calculating computer memory size information of each of the elements in the first direct access storage device.

23. The system of claim 22 further comprising:

means for creating an ordered list in order to extract the size information from the first direct access storage device, wherein each entry of the ordered list is associated with one of the elements of the set; and

means for storing into each entry physical block addresses of one or more memory blocks that store the element associated with the entry.

24. The system of claim 22 further comprising:

means for creating an ordered list in order to extract the size information from the first direct access storage device, wherein each entry of the ordered list is associated with one of the elements of the set;

means for storing into each entry physical cylinder and head (CH) addresses of one or more tracks that store the element associated with the entry.

25. The system of claim 22 further comprising:

means for creating a file system size table, wherein each entry of the size table includes information relating to at least one of fields, key fields and data field for one or more records on one of a plurality of tracks; and

means for updating the file system size table each time a format write I/O command is administered to one of the plurality of tracks.

26. The system of claim 16 further comprising:

means for calculating a computer memory size required in the second direct access storage device to copy each element of the set from the first direct access storage device.

27. The system of claim 16 further comprising:

means for creating a bit array, each bit of the bit array associated with one of the elements of the set; and

means for initializing each bit of the bit array to a first state, wherein the first state of each bit designates that the element associated therewith is not yet copied.

28. The system of claim 27 further comprising:

means for changing the first state of one of bits in the bit array, when the element associated with the one of bits has been copied from the first direct access storage device to the second direct access storage device.

29. The system of claim 16 is further comprising:

means for copying data stored on the snapshot disk to a tape.

30. The system of claim 16, wherein the mean for iterating is further configured to perform the iteration in parallel with respect to the elements.