Relocating item in distributed storage system

• US 20080320005A1
• Filed: 06/19/2007
• Published: 12/25/2008
• Est. Priority Date: 06/19/2007
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: MacCormick, John P., Jager, Marcus J., McCulloch, Douglas J.
• Granted Patent: US 8,560,691 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 16/182 Distributed file systems

Abstract

Techniques are provided for moving an item from one item server to another item server in a distributed storage system, using a location service, APIs, and item states. There are three parties that transact with each other: a source item server, a destination item server, and a location service. Each item stored at the source has a move status, e.g., “stationary”, “source attempting transfer”, “destination accepting transfer”, or “destination attempting transfer”. Similarly, each item stored at the destination also has a move status, e.g., “stationary”, “source attempting transfer”, “destination accepting transfer”, or “destination attempting transfer”. The location service desirably has an entry for every item stored by the storage system. An item'"'"'s entry may comprise the item'"'"'s current location (e.g., an identifier of an item server) together with a state, such as “stable” or “attempting transfer”.

Claims

1. A distributed storage system comprising:

a source server that stores an item and comprises a source item ownership list, the source server maintaining a move status for the item;

a destination server that comprises a destination item ownership list and is capable of receiving the item from the source server, the destination server maintaining a move status for the item; and

a location service that stores an entry for the item, the entry comprising a current location of the item and a state of the item.

2. The system of claim 1, wherein the move status at the source server is stationary, source attempting transfer, destination accepting transfer, or destination attempting transfer, and the move status at the destination server is stationary, source attempting transfer, destination accepting transfer, or destination attempting transfer.

3. The system of claim 2, wherein the move status at the source server changes from stationary to source attempting transfer after the item'"'"'s data is copied to the destination server.

4. The system of claim 2, wherein the move status at the destination server is set to destination accepting transfer after the destination server creates an entry for the item in the destination item ownership list.

5. The system of claim 4, wherein the move status at the destination server is set to destination attempting transfer after a transfer control request is received from the source server.

6. The system of claim 5, wherein the move status at the destination server is set to stationary after the item is successfully stored at the destination server.

7. The system of claim 1, wherein the state of the item in the location service is stable or attempting transfer.

8. The system of claim 7, wherein the state of the item in the location service is set to attempting transfer when the item is being moved from the source server to the destination server.

9. A method of relocating an item in a distributed storage system, comprising:

receiving a request to move an item from a source server to a destination server;

sending a move request to the destination server;

transferring the item to the destination server;

changing a move status of the item at the source server from stationary to source attempting transfer;

transferring control to the destination server; and

deleting the item at the source server.

10. The method of claim 9, wherein transferring the item to the destination server comprises:

transferring preliminary data associated with the item to the destination server;

locking access to the item; and

transferring final data associated with the item to the destination server.

11. The method of claim 9, further comprising checking the state of the item at a location service prior to sending the move request to the destination server, and if the state is not stable, then aborting the method.

12. The method of claim 11, further comprising changing the state of the item at the location service from stable to attempting transfer prior to transferring control to the destination server.

13. The method of claim 9, wherein deleting the item at the source server comprises deleting an item entry in an ownership list associated with the source server.

14. The method of claim 9, further comprising creating an item entry in an ownership list associated with the destination server, and setting a move status of the item at the destination server to destination accepting transfer.

15. The method of claim 14, wherein transferring control to the destination server comprises:

changing the move status of the item at the destination server to destination attempting transfer;

changing the state of the item at a location service from attempting transfer to stable; and

upon receiving an indication that changing the state was successful, changing the move status of the item at the destination server to stationary.

16. A method of relocating an item in a distributed storage system, comprising:

receiving a read state request for an item at a location service in the distributed storage system;

checking the state of the item, the state being stored at the location service; and

transferring the item from a source server to a destination server based on the state of the item.

17. The method of claim 16, wherein the state is stable or attempting transfer.

18. The method of claim 16, wherein if the state is not stable, then aborting the method prior to transferring the item.

19. The method of claim 16, further comprising changing the state of the item at the location service from stable to attempting transfer after transferring the item to the destination server.

20. The method of claim 19, further comprising transferring control to the destination server after changing the state of the item at the location service from stable to attempting transfer.