TRANSACTIONAL VIRTUAL DISK WITH DIFFERENTIAL SNAPSHOTS

• US 20100280996A1
• Filed: 05/04/2009
• Published: 11/04/2010
• Est. Priority Date: 05/04/2009
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: MOKA5, INC.
• Inventors: Gross, IV, Jesse Ernest, Whaley, John, Purtell, II, Thomas Joseph
• Granted Patent: US 8,805,788 B2
• Time in Patent Office: Days
• US Class Current: 707/649
• CPC Class Codes: G06F 11/1451 by selection of backup contents
• CPC Class Codes: G06F 11/1474 in transactions G06F16/20 takes precedence
• CPC Class Codes: G06F 16/188 Virtual file systems
• CPC Class Codes: G06F 21/6218 to a system of files or objects, e.g. local or distributed file system or database
• CPC Class Codes: G06F 2201/815 Virtual middleware or OS functionality using virtual machines to implement generic software techniques for error detection or fault masking G06F11/1484
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/062 Securing storage systems
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/0664 at device level, e.g. emulation of a storage device or system

Abstract

Some embodiments provide a system that provides a virtual disk in a computer system. During operation, the system stores data for the virtual disk in a virtual disk file on the computer system. Next, the system loads a differential location data structure corresponding to a snapshot of the virtual disk into memory on the computer system and processes input/output (I/O) operations to the virtual disk using the differential location data structure and the virtual disk file. Finally, the system periodically generates a new snapshot of the virtual disk by transactionally committing changes made to the differential location data structure by the I/O operations to the virtual disk file.

Claims

1. A computer-implemented method for providing a virtual disk in a computer system, comprising:

storing data for the virtual disk in a virtual disk file on the computer system;

loading a differential location data structure corresponding to a snapshot of the virtual disk into memory on the computer system;

processing input/output (I/O) operations to the virtual disk using the differential location data structure and the virtual disk file; and

periodically generating a new snapshot of the virtual disk by transactionally committing changes made to the differential location data structure by the I/O operations to the virtual disk file.

2. The computer-implemented method of claim 1, further comprising resizing the virtual disk file based on free space on the virtual disk file or filesystem free space associated with a host filesystem on the computer system.

3. The computer-implemented method of claim 1, wherein each of the I/O operations corresponds to a read operation or a write operation.

4. The computer-implemented method of claim 3, wherein processing the read operation involves:

locating a set of blocks requested in the read operation using the differential location data structure; and

retrieving the blocks from the virtual disk file.

5. The computer-implemented method of claim 4, wherein processing the read operation further involves at least one of:

individually decompressing each of the blocks;

individually decrypting each the blocks; and

individually checking a hash associated with each of the blocks.

6. The computer-implemented method of claim 3, wherein processing the write operation involves:

allocating a space on the virtual disk file based on a block size associated with the write operation;

executing the write operation by writing a block to the space; and

updating the differential location data structure using the block.

7. The computer-implemented method of claim 6, wherein processing the write operation further involves at least one of:

compressing the block;

encrypting the block; and

computing a hash associated with the block.

8. The computer-implemented method of claim 1, wherein generating the new snapshot of the virtual disk involves:

identifying the changes made to the differential location data structure;

allocating a space on the virtual disk file for the changes;

writing the changes to the space; and

transactionally committing the changes to the virtual disk file by updating a checkpoint region in the virtual disk file to reference the changes.

9. The computer-implemented method of claim 1, wherein loading the differential location data structure into the memory involves:

populating the differential location data structure in the memory with a most recent full snapshot of the virtual disk from the virtual disk file; and

updating the differential location data structure with one or more differential snapshots of the virtual disk generated after the most recent full snapshot.

10. The computer-implemented method of claim 1, wherein the virtual disk comprises a virtual computing environment executing on the computer system.

11. A system for providing a virtual disk in a computer system, comprising:

a virtual disk file comprising data for the virtual disk;

a differential location data structure corresponding to a snapshot of the virtual disk;

an interceptor configured to process input/output (I/O) operations to the virtual disk using the differential location data structure and the virtual disk file; and

a disk emulator configured to;

load the differential location data structure into memory on the computer system; and

periodically generate a new snapshot of the virtual disk by transactionally committing changes to the differential location data structure to the virtual disk file.

12. The system of claim 11, wherein each of the I/O operations corresponds to a read operation or a write operation.

13. The system of claim 12, wherein processing the read operation involves:

locating a set of blocks requested in the read operation using the differential location data structure; and

retrieving the blocks from the virtual disk file.

14. The system of claim 12, wherein processing the write operation involves:

allocating a space on the virtual disk file based on a block size associated with the write operation;

executing the write operation by writing a block to the space; and

updating the differential location data structure using the block.

15. The system of claim 11, wherein generating the new snapshot of the virtual disk involves:

identifying the changes made to the differential location data structure;

allocating a space on the virtual disk file for the changes;

writing the changes to the space; and

transactionally committing the changes to the virtual disk file by updating a checkpoint region in the virtual disk file to reference the changes.

16. The system of claim 11, wherein loading the differential location data structure into the memory involves:

populating the differential location data structure in the memory with a most recent full snapshot of the virtual disk from the virtual disk file; and

updating the differential location data structure with one or more differential snapshots of the virtual disk generated after the most recent full snapshot.

17. A computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method for providing a virtual disk in a computer system, the method comprising:

storing data for the virtual disk in a virtual disk file on the computer system;

loading a differential location data structure corresponding to a snapshot of the virtual disk into memory on the computer system;

processing input/output (I/O) operations to the virtual disk using the differential location data structure and the virtual disk file; and

periodically generating a new snapshot of the virtual disk by transactionally committing changes made to the differential location data structure by the I/O operations to the virtual disk file.

18. The computer-readable storage medium of claim 17, wherein each of the I/O operations corresponds to a read operation or a write operation.

19. The computer-readable storage medium of claim 18, wherein processing the read operation involves:

locating a set of blocks requested in the read operation using the differential location data structure; and

retrieving the blocks from the virtual disk file.

20. The computer-readable storage medium of claim 18, wherein processing the write operation involves:

allocating a space on the virtual disk file based on a block size associated with the write operation;

executing the write operation by writing a block to the space; and

updating the differential location data structure using the block.