Incremental and differential backups of virtual machine files

• US 8,099,391 B1
• Filed: 03/17/2009
• Issued: 01/17/2012
• Est. Priority Date: 03/17/2009
• Status: Active Grant

• Current Assignee: Veritas Technologies, LLC (Whitehouse Group Ltd.)
• Original Assignee: Symantec Corporation (NortonLifeLock Inc.)
• Inventors: Monckton, Russell David
• Primary Examiner(s): Le, Thu-Nguyet
• Application Number:
  US12/405,777
• Time in Patent Office: 1,036 Days
• Field of Search: 707640-641, 707644-648, 707650-654
• US Class Current: 707/647
• CPC Class Codes: G06F 11/1451 by selection of backup contents
• 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

Abstract

Various embodiments of a system and method for backing up files used by a virtual machine are described herein. The files may be stored within a virtual disk image file. A full backup of the virtual disk image file may first be created. After creating the full backup, one or more incremental or differential backups of the virtual disk image file may be created. In some embodiments, fingerprints of the sectors of the virtual disk image file may be stored and used to identify which sectors should be included in the incremental or differential backups.

Claims

1. A computer-accessible storage medium storing program instructions executable to:

at a first time, create a first backup representation of a virtual disk image file that stores a plurality of files used by a virtual machine, wherein the virtual disk image file represents a plurality of disk sectors, wherein data of the plurality of files is stored across the disk sectors, wherein in creating the first backup representation, the program instructions are executable to;

determine whether each disk sector of the virtual disk image file is in use at the first time by examining metadata of the virtual disk image file;

for each respective disk sector that is in not in use at the first time, store information in association with the first backup representation indicating that the respective disk sector is not in use;

for each respective disk sector that is in use at the first time;

store information with the first backup representation indicating that the respective disk sector is in use;

use the metadata of the virtual disk image file to read data from the respective disk sector;

copy the data from the respective disk sector into the first backup representation;

compute a first fingerprint for the respective disk sector based on the data of the respective disk sector; and

store the first fingerprint for the respective disk sector in association with the first backup representation;

wherein the program instructions are further executable to create a second backup representation of the virtual disk image file at a second time after creating the first backup representation and after a subset of the sectors represented by the virtual disk image file have changed, wherein in creating the second backup representation, the program instructions are executable to;

determine whether each disk sector of the virtual disk image file is in use at the second time by examining the metadata of the virtual disk image file;

for each respective disk sector that is in not in use at the second time, store information in association with the second backup representation indicating that the respective disk sector is not in use;

for each respective disk sector that is in use at the second time;

store information with the second backup representation indicating that the respective disk sector is in use;

use the metadata of the virtual disk image file to read data from the respective disk sector;

compute a new fingerprint for the respective disk sector based on the data of the respective disk sector;

store the new fingerprint in association with the second backup representation;

determine whether the respective disk sector was previously in use at the first time when the first backup representation was created;

if the respective disk sector was not previously in use then copy the data from the respective disk sector into the second backup representation;

if the respective disk sector was previously in use then retrieve the first fingerprint for the respective disk sector stored in association with the first backup representation, compare the new fingerprint to the first fingerprint to determine whether the data of the respective disk sector has changed since the first backup representation was created, and copy the data from the respective disk sector into the second backup representation if the respective disk sector has changed.

2. The computer-accessible storage medium of claim 1,

wherein creating the second backup representation does not include storing in the second backup representation data of sectors that have not changed since the first backup representation was created.

3. The computer-accessible storage medium of claim 1,

wherein the second backup representation is created in response to user input requesting to create one of:

an incremental backup representation of the virtual disk image file;

a differential backup representation of the virtual disk image file.

4. The computer-accessible storage medium of claim 1, wherein the program instructions are further executable to:

after creating the second backup representation, create a third backup representation of the virtual disk image file, wherein creating the third backup representation comprises;

determining whether each sector of the plurality of disk sectors represented by the virtual disk image file has changed since the second backup representation was created; and

for each sector of the plurality of disk sectors that has changed since the second backup representation was created, using the virtual disk image file to read data of the sector, and storing the data of the sector in the third backup representation;

wherein creating the third backup representation does not include storing in the third backup representation data of sectors that have not changed since the second backup representation was created.

5. The computer-accessible storage medium of claim 1, wherein the program instructions are further executable to:

after creating the second backup representation, create a third backup representation of the virtual disk image file, wherein creating the third backup representation comprises;

determining whether each sector of the plurality of disk sectors represented by the virtual disk image file has changed since the first backup representation was created; and

for each sector of the plurality of disk sectors that has changed since the first backup representation was created, using the virtual disk image file to read data of the sector, and storing the data of the sector in the third backup representation;

wherein creating the third backup representation does not include storing in the third backup representation data of sectors that have not changed since the first backup representation was created.

6. The computer-accessible storage medium of claim 1,

wherein the program instructions are executable to store the first fingerprint for the respective disk sector in a database, wherein the first fingerprint is retrieved from the database at the second time when the second backup representation is created.

7. The computer-accessible storage medium of claim 1,

wherein the virtual disk image file is one of:

a Virtual Hard Disk (VHD) file;

a Virtual Machine Disk Format (VMDK) file.

8. The computer-accessible storage medium of claim 1,

wherein the plurality of files includes a first file, wherein a first subset of sectors of the first file is stored in the second backup representation of the virtual disk image file, wherein a second subset of sectors of the first file is not stored in the second backup representation of the virtual disk image file;

wherein the program instructions are further executable to restore the first file using the second backup representation of the virtual disk image file, wherein restoring the first file comprises;

restoring the first subset of sectors of the first file from the second backup representation of the virtual disk image file; and

restoring the second subset of sectors of the first file from the first backup representation of the virtual disk image file.

9. The computer-accessible storage medium of claim 1,

wherein the program instructions are further executable to restore the virtual disk image file using the second backup representation of the virtual disk image file, wherein restoring the virtual disk image file comprises:

for each respective sector of the plurality of disk sectors;

restoring the respective sector from the second backup representation of the virtual disk image file if the second backup representation of the virtual disk image file includes the respective sector;

restoring the respective sector from the first backup representation of the virtual disk image file if the second backup representation of the virtual disk image file does not include the respective sector.

10. A system comprising:

one or more processors; and

memory storing program instructions, wherein the program instructions are executable by the one or more processors to;

at a first time, create a first backup representation of a virtual disk image file that stores a plurality of files used by a virtual machine, wherein the virtual disk image file represents a plurality of disk sectors, wherein data of the plurality of files is stored across the disk sectors, wherein in creating the first backup representation, the program instructions are executable by the one or more processors to;

determine whether each disk sector of the virtual disk image file is in use at the first time by examining metadata of the virtual disk image file;

for each respective disk sector that is in not in use at the first time, store information in association with the first backup representation indicating that the respective disk sector is not in use;

for each respective disk sector that is in use at the first time;

store information with the first backup representation indicating that the respective disk sector is in use;

use the metadata of the virtual disk image file to read data from the respective disk sector;

copy the data from the respective disk sector into the first backup representation;

compute a first fingerprint for the respective disk sector based on the data of the respective disk sector; and

store the first fingerprint for the respective disk sector in association with the first backup representation;

wherein the program instructions are further executable by the one or more processors to create a second backup representation of the virtual disk image file at a second time after creating the first backup representation and after a subset of the sectors represented by the virtual disk image file have changed, wherein in creating the second backup representation, the program instructions are executable to;

determine whether each disk sector of the virtual disk image file is in use at the second time by examining the metadata of the virtual disk image file;

for each respective disk sector that is in not in use at the second time, store information in association with the second backup representation indicating that the respective disk sector is not in use;

for each respective disk sector that is in use at the second time;

store information with the second backup representation indicating that the respective disk sector is in use;

use the metadata of the virtual disk image file to read data from the respective disk sector;

compute a new fingerprint for the respective disk sector based on the data of the respective disk sector;

store the new fingerprint in association with the second backup representation;

determine whether the respective disk sector was previously in use at the first time when the first backup representation was created;

if the respective disk sector was not previously in use then copy the data from the respective disk sector into the second backup representation;

if the respective disk sector was previously in use then retrieve the first fingerprint for the respective disk sector stored in association with the first backup representation, compare the new fingerprint to the first fingerprint to determine whether the data of the respective disk sector has changed since the first backup representation was created, and copy the data from the respective disk sector into the second backup representation if the respective disk sector has changed.

11. The system of claim 10,

wherein creating the second backup representation does not include storing in the second backup representation data of sectors that have not changed since the first backup representation was created.

12. The system of claim 10,

wherein the second backup representation is created in response to user input requesting to create one of:

an incremental backup representation of the virtual disk image file;

a differential backup representation of the virtual disk image file.

13. The system of claim 10, wherein the program instructions are further executable by the one or more processors to:

after creating the second backup representation, create a third backup representation of the virtual disk image file, wherein creating the third backup representation comprises;

determining whether each sector of the plurality of disk sectors represented by the virtual disk image file has changed since the second backup representation was created; and

for each sector of the plurality of disk sectors that has changed since the second backup representation was created, using the virtual disk image file to read data of the sector, and storing the data of the sector in the third backup representation;

wherein creating the third backup representation does not include storing in the third backup representation data of sectors that have not changed since the second backup representation was created.

14. The system of claim 10, wherein the program instructions are further executable by the one or more processors to:

after creating the second backup representation, create a third backup representation of the virtual disk image file, wherein creating the third backup representation comprises;

determining whether each sector of the plurality of disk sectors represented by the virtual disk image file has changed since the first backup representation was created; and

for each sector of the plurality of disk sectors that has changed since the first backup representation was created, using the virtual disk image file to read data of the sector, and storing the data of the sector in the third backup representation;

wherein creating the third backup representation does not include storing in the third backup representation data of sectors that have not changed since the first backup representation was created.

15. The system of claim 10,

wherein the plurality of files includes a first file, wherein a first subset of sectors of the first file is stored in the second backup representation of the virtual disk image file, wherein a second subset of sectors of the first file is not stored in the second backup representation of the virtual disk image file;

wherein the program instructions are further executable by the one or more processors to restore the first file using the second backup representation of the virtual disk image file, wherein restoring the first file comprises;

restoring the first subset of sectors of the first file from the second backup representation of the virtual disk image file; and

restoring the second subset of sectors of the first file from the first backup representation of the virtual disk image file.

16. The system of claim 10,

wherein the program instructions are further executable by the one or more processors to restore the virtual disk image file using the second backup representation of the virtual disk image file, wherein restoring the virtual disk image file comprises:

for each respective sector of the plurality of disk sectors;

restoring the respective sector from the second backup representation of the virtual disk image file if the second backup representation of the virtual disk image file includes the respective sector;

restoring the respective sector from the first backup representation of the virtual disk image file if the second backup representation of the virtual disk image file does not include the respective sector.

17. A computer-implemented method comprising:

at a first time, a computer system creating a first backup representation of a virtual disk image file that stores a plurality of files used by a virtual machine, wherein the virtual disk image file represents a plurality of disk sectors, wherein data of the plurality of files is stored across the disk sectors, wherein creating the first backup representation includes;

determining whether each disk sector of the virtual disk image file is in use at the first time by examining metadata of the virtual disk image file;

for each respective disk sector that is in not in use at the first time, storing information in association with the first backup representation indicating that the respective disk sector is not in use;

for each respective disk sector that is in use at the first time;

storing information with the first backup representation indicating that the respective disk sector is in use;

using the metadata of the virtual disk image file to read data from the respective disk sector;

copying the data from the respective disk sector into the first backup representation;

computing a first fingerprint for the respective disk sector based on the data of the respective disk sector; and

storing the first fingerprint for the respective disk sector in association with the first backup representation;

wherein the method further comprises the computer system creating a second backup representation of the virtual disk image file at a second time after creating the first backup representation and after a subset of the sectors represented by the virtual disk image file have changed, wherein creating the second backup representation includes;

determining whether each disk sector of the virtual disk image file is in use at the second time by examining the metadata of the virtual disk image file;

for each respective disk sector that is in not in use at the second time, storing information in association with the second backup representation indicating that the respective disk sector is not in use;

for each respective disk sector that is in use at the second time;

storing information with the second backup representation indicating that the respective disk sector is in use;

using the metadata of the virtual disk image file to read data from the respective disk sector;

computing a new fingerprint for the respective disk sector based on the data of the respective disk sector;

storing the new fingerprint in association with the second backup representation;

determining whether the respective disk sector was previously in use at the first time when the first backup representation was created;

if the respective disk sector was not previously in use then copying the data from the respective disk sector into the second backup representation;

if the respective disk sector was previously in use then retrieving the first fingerprint for the respective disk sector stored in association with the first backup representation, comparing the new fingerprint to the first fingerprint to determine whether the data of the respective disk sector has changed since the first backup representation was created, and copying the data from the respective disk sector into the second backup representation if the respective disk sector has changed.