Storing Block-Level Tracking Information in the File System on the Same Block Device

• US 20100076934A1
• Filed: 11/12/2009
• Published: 03/25/2010
• Est. Priority Date: 08/25/2008
• Status: Active Grant

• Current Assignee: Vmware LLC (Broadcom, Inc.)
• Original Assignee: VMware, Inc. (Broadcom, Inc.)
• Inventors: PERSHIN, Aleksey, PIDURI, Sudarsan R.
• Granted Patent: US 8,615,489 B2
• Time in Patent Office: Days
• US Class Current: 707/640
• CPC Class Codes: G06F 11/1441 Resetting or repowering
• CPC Class Codes: G06F 11/1451 by selection of backup contents

Abstract

Writes to a storage device of a protected computer system are tracked in a manner that accounts for those writes that may occur during a system reboot process when the file system is not available. During the shutdown process, write tracking data is maintained in system memory and is written into storage locations allocated to the tracking file after the file system has been dismounted so that any writes that may occur during the file system dismount can be captured. During the boot process, temporary write tracking data is maintained in system memory even before the file system is mounted so that any writes that may occur immediately after the file system mount can be captured. The temporary write tracking data is later merged with the tracking data contained in the tracking file and the merged tracking data is used to track further writes to the storage device.

Claims

1. In a computer system having a processing unit, system memory, and a storage device, the computer system being configured with a file system and a bitmap driver for tracking writes to the storage device by updating tracking data stored in the system memory, a method of tracking writes to the storage device during a shutdown process of the computer system which includes dismounting of the file system, said method comprising:

prior to dismounting the file system in connection with the shutdown process, allocating a tracking file to be stored in the storage device; and

after dismounting the file system, storing the tracking data into storage locations in the storage device that have been allocated to the tracking file,

wherein, upon reboot of the computer system, the tracking file stored in the storage device is loaded into the system memory for use by the bitmap driver in tracking further writes to the storage device.

2. The method according to claim 1, further comprising:

upon allocating the tracking file, determining the storage locations in the storage device that have been allocated to the tracking file and saving the storage locations in the system memory.

3. The method according to claim 1, wherein the tracking data comprises a bitmap of blocks of the storage device.

4. The method according to claim 3, further comprising:

storing tracking parameters in an operating system configuration file,

wherein the stored tracking parameters are read from the operating system configuration file upon reboot of the computer system.

5. The method according to claim 4, wherein the tracking parameters include a block size.

6. The method according to claim 4, wherein the tracking parameters include a block offset.

7. The method according to claim 3, wherein the storage device is configured with multiple volumes and the tracking data includes a separate bitmap for each of the volumes that are being tracked.

8. In a computer system having a processing unit, system memory, and a storage device, the computer system being configured with a file system and a bitmap driver for tracking writes to the storage device by updating tracking data stored in the system memory, a method of tracking writes to the storage device during a boot process of the computer system which includes mounting of the file system, said method comprising:

prior to mounting the file system in connection with the boot process, tracking writes to the storage device by updating a first tracking data stored in the system memory; and

after mounting the file system, loading the tracking file into the system memory as a second tracking data, merging the first tracking data and the second tracking data, and tracking further writes to the storage device by updating the merged tracking data.

9. The method according to claim 8, further comprising:

reading tracking parameters including a block offset and a block size from an operating system configuration file; and

updating the first tracking data in accordance with the block offset and the block size.

10. The method according to claim 9, wherein the storage device is configured with multiple volumes and the tracking parameters includes a separate block offset and a separate block size for each of the volumes that are being tracked.

11. The method according to claim 8, wherein the first tracking data is updated in accordance with an assumed block offset and an assumed block size, and the merging of the first tracking data and the second tracking data corrects for any differences in the assumed offset and the assumed block size and an actual block offset and an actual block size.

12. The method according to claim 8, wherein the storage device is configured with multiple volumes and the first tracking data includes a separate bitmap for each of the volumes and the second tracking data includes a separate bitmap for each of the volumes that are being tracked.

13. The method according to claim 12, wherein the number of bitmaps in the first tracking data is greater than the number of bitmaps in the second tracking data.

14. The method according to claim 13, wherein:

the tracking file contains information about which multiple volumes are being tracked;

prior to loading the tracking file into the system memory, writes to all of the multiple volumes are tracked by updating the bitmap for each of the multiple volumes; and

after loading the tracking file into the system memory and before merging, discarding the bitmap for the volumes that are not being tracked.

15. A computer backup system, comprising:

a first computer system having a system memory and a storage device; and

a second computer system having a system memory and a virtual machine that is configured to be a backup of the first computer system,

wherein the first computer system is configured with a file system and a bitmap driver for tracking writes to the storage device by updating tracking data stored in the system memory, the tracking data indicating blocks of the storage device that have been modified since a last backup cycle, and

wherein the bitmap driver is configured to track writes to the storage device during a shutdown process and a reboot process of the first computer system by;

(i) committing the tracking data to storage locations of a tracking file stored in the storage device after the file system is dismounted in connection with the shutdown process, and (ii) after the reboot process is initiated, tracking writes to the storage device prior to loading the tracking file into the system memory.

16. The system according to claim 15, wherein the first computer system is housed in a first datacenter and the second computer system is housed in a second datacenter that is physically separated by a distance sufficient to qualify for disaster recovery.

17. The system according to claim 15, wherein the storage device is configured with multiple volumes and the tracking data comprises a bitmap of blocks of the volumes that are being tracked.

18. The system according to claim 17, wherein the tracking file contains information about which multiple volumes are being tracked.

19. The system according to claim 15, wherein:

after the reboot process is initiated and prior to loading the tracking file into the system memory, the bitmap driver tracks writes to the storage device by updating a temporary tracking data stored in the system memory; and

after loading the tracking file into the system memory, the bitmap driver tracks writes to the storage device by updating a merged tracking data stored in the system memory, the merged tracking data being formed by merging the temporary tracking data and a tracking data contained in the tracking file.

20. The system according to claim 19, wherein the storage device is configured with multiple volumes and the temporary tracking data includes a separate bitmap for each of the volumes and the tracking data contained in the tracking file includes a separate bitmap for each of the volumes that are being tracked.