Granted Patent B1

US 6,996,687 · App. 10/324,812 · Granted Feb 7, 2006

Abstract

Claims (67)

1. A computer readable medium comprising instructions executable by a computer system, wherein the computer system implements a method in response to executing the instructions, the method comprising:

creating a primary data volume;

creating a first virtual copy of the primary data volume;

modifying first data of the primary data volume after creation of the first virtual copy thereof;

creating a second virtual copy of the primary data volume after modification of the first data thereof;

generating a write-data transaction for modifying second data of the primary data volume, wherein the write-data transaction is generated after creation of the second virtual copy;

copying the second data of the primary data volume to memory allocated to store data of the second virtual copy;

modifying the second data of the primary data volume after the second data is copied to the memory allocated to store data of the second virtual copy;

copying a third virtual copy of the primary data volume after modification of the second data thereof;

wherein, before the second data of the primary volume is modified, the second data is copied only to the memory allocated to store data of the second virtual copy.

2. The computer readable medium of claim 1 wherein the method further comprises:

after the second data of the primary volume is modified, copying the second data stored

in memory allocated to stroe data of the second virtual copy to memory allocated to store data of the first virtual copy.

3. The computer readable medium of claim 1 wherein the method further comprises:

generating a read-data transaction for reading data from one of the first, second, or third

virtual copies; accessing memoryy allocated to store data of the primary data volume in response to generating the read-data transaction; reading data from the accessed memory.

4. The computer readable medium of claim 1 wherein the method further comprises:

generating a read-data transaction for reading data from one of the first, second, or third

virtual copies; accessing memory allocated to store data of the second virtual copy in response to

generating the read-data transaction; reading data from the accessed memory.

5. The computer readable medium of claim 1 wherein the method further comprises:

generating a read-data transaction for reading data from one of the first, second, or third

virtual copies; accessing memory allocated to store data of the third virtual copy in response to

generating the read-data transaction; reading data from the accessed memory.

6. The computer readable medium of claim 1 wherein the method further comprises:

generating a write-data transaction for modifying data of the first or second virtual coies;

copying data stored in the memory allocated to store data of the third virtual copy to

memory allocated to store data of the first or second virtual copies; modifying the data copied to memory allocated to store data of the first or second virtual copies.

7. An apparatus comprising:

a primary memory for storing a primary data volume;

first, second, and third secondary memories;

means for creating a first virtual copy of the primary data volume;

means for modifying first data of the primary data volume after creation of the first virtual copy thereof;

means for creating a second virtual copy of the primary data volume after modification of the first data thereof;

means for generating a write-data transaction for modifying second data of the modified primary data volume, wherein the write-data transaction is generated after creation of the second virtual copy;

means for generating a third virtual copy of the primary data volume after modification of the second data thereof;

means for allocating the first, second, and third secondary memories to store data of the first, second, and third virtual copies, respectively;

means for copying the second data of the modified primary data volume to the second secondary memory;

means for modifying the second data of the modified primary data volume after the second data is copied to the second secondary memory; wherein, before the second data of the primary data volume is modified, the second data is copied only to the second memory.

8. The apparatus of claim 7 further comprising means for copying the second data stored in the second secondary memory to the first secondary memory after the second data of the primary volume is modified.

9. A method comprising:

creating a primary data volume;

creating a first virtual copy of the primary data volume;

modifying first data of the primary data volume after creation of the first virtual copy thereof;

creating a second virtual copy of the primary data volume after modification of the first data thereof;

generating a write-data transaction for modifying second data of the primary data volume, wherein the write-data transaction is generated after creation of the second virtual copy; copying the second data of the primary data volume to memory allocated to store data of the second virtual copy;

modifying the second data of the primary data volume after the second data is copied to the memory allocated to store data of the second virtual copy; creating a third virtual copy of the primary data volume after modification of the second data thereof;

wherein, before the second data of the primary volume is modified, the second data is copied only to the memory allocated to store data of the second virtual copy.

10. The method of claim 9 further comprising:

after the second data of the primary volume is modified, copying the second data stored in memory allocated to store data of the second virtual copy to memory allocated to store data of the first virtual copy.

11. The method of claim 9 further comprising:

generating a read-data transaction for reading data from one of the first, second, or third virtual copies;

accessing memory allocated to store data of the primary data volume in response to generating the read-data transaction;

reading data from the accessed memory.

12. The method of claim 9 further comprising:

generating a read-data transaction for reading data from one of the first, second, or third virtual copies;

accessing memory allocated to store data of the second virtual copy in response to generating the read-data transaction;

reading data from the accessed memory.

13. The method of claim 9 further comprising:

generating a read-data transaction for reading data from one of the first, second, or third virtual copies;

accessing memory allocated to store data of the third virtual copy in response to generating the read-data transaction;

reading data from the accessed memory.

14. The method of claim 9 wherein the method further comprises:

generating a write-data transaction for modifying data of the first or second virtual coies;

copying data stored in the memory allocated to store data of the third virtual copy to

memory allocated to store data of the first or second virtual copies;

modifying the data copied to memory allocated to store data of the first or second virtual copies.

Assignments (17)