CLUSTERED FILESYSTEM WITH DATA VOLUME SNAPSHOT MAINTENANCE

• US 20120191654A1
• Filed: 04/09/2012
• Published: 07/26/2012
• Est. Priority Date: 06/05/2001
• Status: Active Grant

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Silicon Graphics International Corporation (Hewlett-Packard Enterprise Company)
• Inventors: Beck, Kenneth
• Granted Patent: US 8,527,463 B2
• Time in Patent Office: Days
• US Class Current: 707/639
• CPC Class Codes: G06F 11/2064 while ensuring consistency
• CPC Class Codes: G06F 11/2082 Data synchronisation
• CPC Class Codes: G06F 16/10 File systems; File servers
• CPC Class Codes: G06F 16/128 Details of file system snapshots on the file-level, e.g. snapshot creation, administration, deletion use of snapshots for error detection or correction G06F11/14, G06F11/16
• CPC Class Codes: G06F 16/182 Distributed file systems
• CPC Class Codes: G06F 2201/84 Using snapshots, i.e. a logical point-in-time copy of the data
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]
• CPC Class Codes: H04L 67/10 in which an application is distributed across nodes in the network software deployment G06F8/60; multiprogramming arrangements G06F9/46
• CPC Class Codes: H04L 67/1097 for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS]
• CPC Class Codes: H04L 67/564 Enhancement of application control based on intercepted application data
• CPC Class Codes: H04L 67/566 Grouping or aggregating service requests, e.g. for unified processing
• CPC Class Codes: H04L 9/40 Network security protocols
• CPC Class Codes: Y10S 707/966 Distributed

Abstract

A computer system with read/write access to storage devices creates a snapshot of a data volume at a point in time while continuing to accept access requests to the mirrored data volume by copying before making changes to the base data volume. Multiple snapshots may be made of the same data volume at different points in time. Only data that is not stored in a previous snapshot volume or in the base data volume are stored in the most recent snapshot volume.

Claims

1. A method of maintaining a copy of at least one data volume in a computer system for at least one point in time, comprising:

initiating creation of a first snapshot of a base volume;

establishing a first repository for the first snapshot of the base volume;

creating a modified region map, the modified region map including a bit representing each region of the base volume, each bit indicating whether any data in a region has changed;

monitoring the base volume for write operations thereto;

identifying a write operation to a first region of the base volume;

determining whether the modified region map indicates that data has changed in the first region since initiation of the first snapshot; and

prior to a write operation to the first region of the base volume, copying the first region of the base volume to the first repository in response to an indication by the modified region map that data in the first region has not been changed since initiation of the first snapshot.

2. The method of claim 1, further comprising:

performing the write operation to the first region of the base volume;

setting a bit in the modified region map corresponding to the first region of the base volume in response to completing the write operation to the first region of the base volume.

3. The method of claim 1, further comprising:

performing the write operation to the base volume without copying in response to an indication by the modified region map that data in the first region has been changed since initiation of the first snapshot.

4. The method of claim 1, further comprising:

receiving a read request for the first snapshot;

providing regions of the base volume that have changed from the first snapshot in the first repository in response to the read request;

providing regions of the base volume that have not changed from the base volume in response to the read request.

5. The method of claim 1, further comprising:

initiating creation of a second snapshot of the base volume;

establishing a second repository for the second snapshot of the base volume;

resetting the modified region map upon initiating the second snapshot.

6. The method of claim 5, further comprising:

monitoring the base volume for write operations thereto;

identifying a write operation to a second region of the base volume;

determining whether the modified region map indicates that data has changed in the second region since initiation of the second snapshot; and

prior to a write operation to the second region of the base volume, copying the second region of the base volume to the second repository in response to an indication by the modified region map that data in the second region has not been changed since initiation of the second snapshot.

7. The method of claim 1, further comprising:

upon reinitialization of a system maintaining the first repository, rebuilding the modified region map to determine if bits should be set corresponding to regions for which a write operation was completed prior to interruption of the system.

14. The system of claim 1, further comprising:

upon reinitialization of a device maintaining the first repository, rebuilding the modified region map to determine if bits should be set corresponding to regions for which a write operation was completed prior to interruption of the device.

8. A system for maintaining a copy of at least one data volume in a computer system for at least one point in time, comprising:

means for initiating creation of a first snapshot of a base volume;

means for establishing a first repository for the first snapshot of the base volume;

means for creating a modified region map, the modified region map including a bit representing each region of the base volume, each bit indicating whether any data in a region has changed;

means for monitoring the base volume for write operations thereto;

means for identifying a write operation to a first region of the base volume;

means for determining whether the modified region map indicates that data has changed in the first region since initiation of the first snapshot; and

prior to a write operation to a first region of the base volume, means for copying the first region of the base volume to the first repository in response to an indication by the modified region map that data in the first region has not been changed since initiation of the first snapshot.

9. The system of claim 8, further comprising:

means for performing the write operation to the first region of the base volume;

means for setting a bit in the modified region map corresponding to the first region of the base volume in response to completing the write operation to the first region of the base volume.

10. The system of claim 8, further comprising:

means for performing the write operation to the base volume without copying in response to an indication by the modified region map that data in the first region has been changed since initiation of the first snapshot.

11. The system of claim 8, further comprising:

means for receiving a read request for the first snapshot;

means for providing regions of the base volume that have changed from the first snapshot in the first repository in response to the read request;

means for providing regions of the base volume that have not changed from the base volume in response to the read request.

12. The system of claim 8, further comprising:

means for initiating creation of a second snapshot of the base volume;

means for establishing a second repository for the second snapshot of the base volume;

means for resetting the modified region map upon initiating the second snapshot.

13. The system of claim 12, further comprising:

means for monitoring the base volume for write operations thereto;

means for identifying a write operation to a second region of the base volume;

means for determining whether the modified region map indicates that data has changed in the second region since initiation of the second snapshot; and

prior to a write operation to the second region of the base volume, means for copying the second region of the base volume to the second repository in response to an indication by the modified region map that data in the second region has not been changed since initiation of the second snapshot.

15. A computer readable storage medium including code for maintaining a copy of at least one data volume in a computer system for at least one point in time, the code when executed operable to:

initiate creation of a first snapshot of a base volume;

establish a first repository for the first snapshot of the base volume;

create a modified region map, the modified region map including a bit representing each region of the base volume, each bit indicating whether any data in a region has changed;

monitor the base volume for write operations thereto;

identify a write operation to a first region of the base volume;

determine whether the modified region map indicates that data has changed in the first region since initiation of the first snapshot; and

prior to a write operation to the first region of the base volume, copy the first region of the base volume to the first repository in response to an indication by the modified region map that data in the first region has not been changed since initiation of the first snapshot.

16. The computer readable storage medium of claim 15, wherein the code is further operable to:

perform the write operation to the first region of the base volume;

set a bit in the modified region map corresponding to the first region of the base volume in response to completing the write operation to the first region of the base volume.

17. The computer readable storage medium of claim 15, wherein the code is further operable to:

receive a read request for the first snapshot;

provide regions of the base volume that have changed from the first snapshot in the first repository in response to the read request;

provide regions of the base volume that have not changed from the base volume in response to the read request.

18. The computer readable storage medium of claim 15, wherein the code is further operable to:

initiate creation of a second snapshot of the base volume;

establish a second repository for the second snapshot of the base volume;

reset the modified region map upon initiating the second snapshot.

19. The computer readable storage medium of claim 18, wherein the code is further operable to:

monitor the base volume for write operations thereto;

identify a write operation to a second region of the base volume;

determine whether the modified region map indicates that data has changed in the second region since initiation of the second snapshot; and

prior to a write operation to the second region of the base volume, copy the second region of the base volume, to the second repository in response to an indication by the modified region map that data in the second region has not been changed since initiation of the second snapshot.

20. The computer readable storage medium of claim 15, wherein the code is further operable to:

upon reinitialization of a system maintaining the first repository, rebuild the modified region map to determine if bits should be set corresponding to regions for which a write operation was completed prior to interruption of the system.