NAMESPACE MIRRORING IN AN EXPANDABLE STORAGE VOLUME

• US 20140330787A1
• Filed: 05/01/2013
• Published: 11/06/2014
• Est. Priority Date: 05/01/2013
• Status: Active Grant

• Current Assignee: NetApp, Inc.
• Original Assignee: NetApp, Inc.
• Inventors: MODUKURI, KIRAN KUMAR, CHEN, SU
• Granted Patent: US 9,684,571 B2
• Time in Patent Office: Days
• US Class Current: 707/659
• CPC Class Codes: G06F 11/1435 using file system or storage system metadata
• CPC Class Codes: G06F 11/20 using active fault-masking, e.g. by switching out faulty elements or by switching in spare elements
• CPC Class Codes: G06F 11/2056 by mirroring
• CPC Class Codes: G06F 2201/84 Using snapshots, i.e. a logical point-in-time copy of the data

Abstract

Technology for maintaining a backup of namespace metadata of an expandable storage volume is disclosed. In various embodiments, the expandable storage volume backs up metadata of a namespace constituent volume of the expandable storage volume into a namespace mirror volume. The namespace constituent volume is responsible for storing the metadata for data objects stored in multiple data constituent volumes of the expandable storage volume. In response to a signal indicating that the namespace constituent volume is unavailable, the namespace mirror volume replaces the role of the namespace constituent volume. The new namespace constituent volume continues to provide metadata for a data object of the data objects in response to an operation request for the data object.

Claims

1. A method, comprising:

backing up metadata of a namespace constituent volume into a namespace mirror volume, wherein the namespace constituent volume stores the metadata for data objects stored in data constituent volumes;

in response to a signal indicating that the namespace constituent volume is unavailable, redirecting metadata requests to the namespace mirror volume instead of the namespace constituent volume; and

providing metadata for a data object of the data objects from the namespace mirror volume in response to an operation request for the data object.

2. The method of claim 1, wherein the backing up comprises:

copying a redirector object for a data object from the namespace constituent volume to the namespace mirror volume, wherein the redirector object includes an object locator indicating a location of the data object within a data constituent volume of the data constituent volumes.

3. The method of claim 1, further comprising:

determining whether to provide metadata for a data object of the data objects from the namespace constituent volume or from the namespace mirror volume, by comparing a frequency of read and write operations on the namespace constituent volume and a frequency of read and write operations on the namespace mirror volume.

4. The method of claim 1, wherein said backing up comprises:

backing up metadata of a namespace constituent volume into a namespace mirror volume according to a predetermined schedule.

5. The method of claim 1, wherein an expandable storage volume includes the namespace constituent volume, the namespace mirror volume, and the data constituent volumes.

6. The method of claim 1, wherein the metadata are organized as inode files stored in the namespace constituent volume, and each of the inode files includes metadata for a data object of the data objects.

7. The method of claim 1, wherein the data constituent volume are flexible volumes.

8. The method of claim 1, further comprising:

creating a new namespace mirror volume by backing up the metadata of the namespace mirror volume that replaces the namespace constituent volume.

9. The method of claim 1, wherein the namespace mirror volume locates in a high-availability pair separate from another high-availability pair that contains the namespace constituent volume.

10. The method of claim 1, wherein the namespace mirror volume locates in an aggregate within a high-availability pair separate from another aggregate within the high-availability pair that contains the namespace constituent volume.

11. The method of claim 5, further comprising:

in response to an operation to set the expandable storage volume offline, stopping backing up the metadata of the namespace constituent volume to the namespace mirror volume.

12. The method of claim 1, further comprising:

identifying a stub file for the data object based on the metadata for the data object; and

locating the data object based on an object locator stored in the stub file.

13. The method of claim 1, further comprising:

adjusting a backup schedule in response to a user instruction, wherein the metadata of the namespace constituent volume is backed up into a namespace mirror volume according to the schedule.

14. The method of claim 1, wherein said backing up comprises:

backing up a portion of metadata of a namespace constituent volume into a namespace mirror volume, wherein the portion of the metadata corresponds to an active file system including multiple data constituent volumes.

15. A computer-readable storage medium storing instructions that, during operation, cause a computing device to perform a process comprising:

in response to an instruction for generating a snapshot for an expandable storage volume, generating snapshots for a namespace constituent volume and multiple data constituent volumes of the expandable storage volume;

in response to an instruction for restoring the expandable storage volume, copying metadata in the snapshot of the namespace constituent volume to the namespace constituent volume of the expandable storage volume, and restoring the data constituent volumes to the snapshots for the data constituent volumes; and

creating a namespace mirror volume as a backup for the restored namespace constituent volume.

16. The computer-readable storage medium of claim 15, wherein the snapshot for the expandable storage volume does not includes a snapshot of the namespace mirror volume.

17. The computer-readable storage medium of claim 15, wherein the process further includes:

backing up metadata of the namespace constituent volume into the namespace mirror volume, wherein the namespace constituent volume stores the metadata for data objects stored in the data constituent volumes.

18. The computer-readable storage medium of claim 15, wherein the namespace constituent volume includes inode files for data objects stored in the data constituent volumes, the nodes files include pointers to stub files, and the sub files maintain object locator for identifying aggregates and storage nodes that store the data objects.

19. The computer-readable storage medium of claim 15, wherein the process further includes:

simultaneously providing metadata for data objects from the namespace mirror volume and the namespace constituent volume in response to operation requests for the data objects.

20. A storage node configured to operate as one of multiple nodes of a network storage cluster, the node comprising:

a network interface via which the node can communicate with other nodes within the network storage cluster and a client computing device;

a component configured to back up metadata of a namespace constituent volume into a namespace mirror volume, wherein the namespace constituent volume stores the metadata for data objects stored in multiple data constituent volumes;

a component configured in response to a signal indicating that the namespace constituent volume is unavailable, redirecting multiple metadata requests to the namespace mirror volume instead of the namespace constituent volume; and

providing metadata for a data object of the data objects from the namespace mirror volume in response to an operation request for the data object.

21. The node of claim 20, wherein an expandable storage volume includes the namespace constituent volume, the namespace mirror volume, and the data constituent volumes, and each data constituent volume of the data constituent volumes is stored in a node of the nodes of the network storage cluster.

22. The node of claim 20, wherein the metadata for the data objects include pointers to stub files, and the stub files include object locators pointing to locations storing content of the data objects.