Method and apparatus for storage unit replacement according to array priority

• US 6,571,354 B1
• Filed: 12/15/1999
• Issued: 05/27/2003
• Est. Priority Date: 12/15/1999
• Status: Expired due to Term

• Current Assignee: Dell Products LP (Dell Technologies Inc.)
• Original Assignee: Dell Products LP (Dell Technologies Inc.)
• Inventors: Taylor, James A., Taylor, Alastair, Parks, Ronald L.
• Primary Examiner(s): Beausoliel, Robert
• Assistant Examiner(s): Duncan, Marc M
• Application Number:
  US09/461,779
• Time in Patent Office: 1,259 Days
• Field of Search: 714/7, 714/5, 714/8, 714/42
• US Class Current: 714/6.32
• CPC Class Codes: G06F 11/008 Reliability or availability analysis

Abstract

A method and apparatus used in a storage network facilitates the protection of data in, and replacement of, storage devices about to fail before the failure happens. In a network that includes a plurality of sets of storage devices which store respective data sets, a storage device about to fail in one set can be replaced by another storage device from another set of storage devices which is being used to store data having a lower priority. The method comprises assigning priorities to sets of storage devices in the network which store respective data sets. In addition, the method includes detecting a condition of a first particular storage device in a particular set of storage devices that has a first priority. Conditions which are detected according to various embodiments indicate that the first particular storage device is suffering events indicating that it is likely to fail, or otherwise suffering from reduced performance. The conditions are detected for example, by the receipt of a signal from the storage device itself, or by the monitoring of statistics concerning the performance of the storage device. The method further provides for selecting a second particular storage device in a second particular set of storage devices having a second priority, which can be used in place of the first particular storage device. In response to detecting the condition, the data set stored in the first particular storage device is migrated to the second particular storage device, and the second particular storage devices identified as a member of the first particular set. The first particular storage device can be gracefully removed from the network, while only affecting the performance of the data access in the lower priority second particular set of storage devices.

Claims

1. A method for managing data in a network, comprising:

detecting a condition of a first particular storage device in a particular set of storage devices in a plurality of sets of storage devices;

selecting a second particular storage device in second particular set of storage devices in the plurality of sets of storage devices;

in response to said detecting a condition, migrating the data set stored in the first particular storage device to the second particular storage device and identifying the second particular storage device as a member of the first particular set; and

,

determining whether a spare device is available for use in the first particular set of storage devices, and if a spare device is not available, then enabling said migrating the data set to the second particular storage device.

2. The method of claim 1, including:

assigning priorities to sets of storage devices in a plurality of sets of storage devices in the network which store respective data sets, and wherein the step of selecting is responsive to the assigned priorities.

3. The method of claim 1, wherein said detecting a condition comprises receiving a signal from said first particular device.

4. The method of claim 1, wherein said condition comprises an event indicating that the first particular device may fail.

5. A method for managing data in a network, comprising:

detecting a condition of a first particular storage device in a particular set of storage devices in a plurality of sets of storage devices;

selecting a second particular storage device in second particular set of storage devices in the plurality of sets of storage devices; and

in response to said detecting a condition, migrating the data set stored in the first particular storage device to the second particular storage device and identifying the second particular storage device as a member of the first particular set, the migrating including

providing an intermediate device in the network coupled to the first particular device and the second particular device;

transferring copies of blocks of data from the data set stored in the first particular device to a buffer in the intermediate device;

transferring the copies of blocks from the buffer to the second particular device;

the transferring of copies of blocks including;

(i) setting a parameter indicating a size and location of the data set;

(ii) generating a request to copy a block from the data set to a buffer in the intermediate device;

(iii) generating a request to transfer the block from the buffer to the second device;

(iv) setting a parameter indicating blocks from the data set stored in the second device; and

(v) repeating the steps (ii) through (iv), until a copy of the data set is stored in the second device; and

,

fulfilling data access requests to the data set during said first and second transferring via the intermediate device.

6. The method of claim 5, including maintaining a data structure in the intermediate device storing a parameter indicating an extent of the data set already transferred to the second particular device.

7. The method of claim 6, wherein the data access requests include a write request to write data to a location in the data set, and including transferring a write request to the first particular device if the location is outside said extent.

8. The method of claim 6, wherein the data access requests include a write request to write data to a location in the data set, and including transferring a write request to the second particular device if the location is inside said extent.

9. The method of claim 6, wherein the data access requests include a write request to write data to a location in the data set, and including transferring a write request to the first particular device and to the second particular device if the location is inside said extent.

10. The method of claim 5, including assigning a priority to the transferring of data access requests relative to the transferring copies of blocks.

11. The method of claim 5, including assigning a higher priority to the transferring of data access requests than to the transferring of copies of blocks.

12. The method of claim 5, wherein the transferring of copies of blocks comprises a background process without blocking data access requests from the client.

13. An intermediate device for a storage network, comprising:

a plurality of communication interfaces, the plurality of communication interfaces adapted for communication with a plurality of sets of storage devices storing a corresponding plurality of data sets, and for communication with one or more clients issuing data access requests for access to the plurality of data sets;

data transfer resources coupled to the plurality of communication interfaces which transfer data access requests identifying a particular data set among the plurality of communication interfaces; and

a logic engine, coupled to the plurality of communication interfaces, which identifies members of the plurality of sets of storage devices, and in response to detection of a condition of a first particular storage device in a particular set of storage devices in the plurality of sets of storage devices, migrates the data set stored in the first particular storage device to a second particular storage device in a second particular set of storage devices in the plurality of sets of storage devices and identifies the second particular storage device as a member of the first particular set.

14. The intermediate device of claim 13, including data structures by which priorities are assigned to sets of storage devices in the plurality of sets of storage devices and wherein the logic engine is responsive to the assigned priorities.

15. The intermediate device of claim 13, wherein the plurality of driver modules includes one or more hardware driver modules to manage respective communication interfaces, and one or more internal driver modules to perform data path tasks independently of the plurality of communication interfaces.

16. The intermediate device of claim 13, wherein the logic engine comprises data structures which store status information concerning said migrating.

17. The intermediate device of claim 13, comprising data structures which store status information concerning progress of said migrating, including a parameter indicating an extent of the data set which already copied to the second storage device.

18. The intermediate device of claim 13, wherein said detection of a condition comprises reception of a signal from said first particular device.

19. The intermediate device of claim 13, wherein said condition comprises an event indicating that the first particular device may fail.

20. An intermediate device for a storage network, comprising:

a plurality of communication interfaces, the plurality of communication interfaces adapted for communication with a plurality of sets of storage devices storing a corresponding plurality of data sets, and for communication with one or more clients issuing data access requests for access to the plurality of data sets;

data transfer resources coupled to the plurality of communication interfaces which transfer data access requests identifying a particular data set among the plurality of communication interfaces; and

a logic engine, coupled to the plurality of communication interfaces, which identifies members of the plurality of sets of storage devices, and in response to detection of a condition of a first particular storage device in a particular set of storage devices in the plurality of sets of storage devices, migrates the data set stored in the first particular storage device to a second particular storage device in a second particular set of storage devices in the plurality of sets of storage devices and identifies the second particular storage device as a member of the first particular set, said logic engine including resources which before selecting the second particular storage device from the second particular set, determine whether a spare device is available for use in the first particular set of storage devices, and if a spare device is not available, then select the second particular storage device.

21. An intermediate device for a storage network, comprising:

a plurality of communication interfaces, the plurality of communication interfaces adapted for communication with a plurality of sets of storage devices storing a corresponding plurality of data sets, and for communication with one or more clients issuing data access requests for access to the plurality of data sets;

data transfer resources coupled to the plurality of communication interfaces which transfer data access requests identifying a particular data set among the plurality of communication interfaces; and

a logic engine, coupled to the plurality of communication interfaces, which identifies members of the plurality of sets of storage devices, and in response to detection of a condition of a first particular storage device in a particular set of storage devices in the plurality of sets of storage devices, migrates the data set stored in the first particular storage device to a second particular storage device in a second particular set of storage devices in the plurality of sets of storage devices and identifies the second particular storage device as a member of the first particular set, wherein said migrating comprises;

transferring copies of blocks of data from the data set stored in the first particular device to a buffer;

transferring the copies of blocks from the buffer to the second particular device the transferring of copies of blocks including;

(i) setting a parameter indicating a size and location of the data set;

(ii) generating a request to copy a block fiom the data set to a buffer in the intermediate device;

(iii) generating a request to transfer the block from the buffer to the second device;

(iv) setting a parameter indicating blocks from the data set stored in the second device; and

(v) repeating the steps (ii) through (iv), until a copy of the data set is stored in the second device; and

,

fulfilling data access requests to the data set during said first and second transferring via the intermediate device.

22. The intermediate device of claim 21, wherein the logic engine maintains a data structure in the intermediate device storing a parameter indicating an extent of the data set already transferred to the second particular device.

23. The intermediate device of claim 22, wherein the data access requests include a write request to write data to a location in the data set, and the logic engine transfers a write request to the first particular device if the location is outside said extent.

24. The intermediate device of claim 22, wherein the data access requests include a write request to write data to a location in the data set, and the logic engine transfers a write request to the second particular device if the location is inside said extent.

25. The intermediate device of claim 22, wherein the data access requests include a write request to write data to a location in the data set, and the logic engine transfers a write request to the first particular device and to the second particular device if the location is inside said extent.

26. The intermediate device of claim 21, wherein the logic engine assigns a priority the transferring of data access requests relative to the transferring copies of blocks.

27. The intermediate device of claim 21, wherein the logic engine assigns a higher priority to the transferring of data access requests than to the transferring of copies of blocks.

28. The intermediate device of claim 21, wherein the transferring of copies of blocks comprises a background process without blocking data access requests from the client.

29. A storage server comprising:

a plurality of communication interfaces, the plurality of communication interfaces adapted for communication with a plurality of sets of storage devices storing a corresponding plurality of data sets, and for communication with one or more clients issuing data access requests for access to the plurality of data sets;

data processing resources coupled with the plurality of communication interfaces which transfer data among the plurality of communication interfaces, the resources including;

a plurality of hardware driver modules to manage respective communication interfaces in the plurality of communication interfaces;

a plurality of internal driver modules to perform data path tasks, independently of the plurality of communication interfaces;

configurable logic linking driver modules in the plurality of hardware driver modules and the plurality of internal driver modules into data paths, the data paths including respective sets of one or more hardware driver modules and one or more internal driver modules;

a protocol server module coupled with the data paths, for a protocol supported on a communication interface in the plurality of communication interfaces, the protocol server recognizing target identifiers in a session according to the protocol and linking the session to a data path in response to the target identifiers; and

a logic engine which identifies members of the plurality of sets of storage devices and in response to detection of a condition of a first particular storage device in a particular set of storage devices in the plurality of sets of storage devices, identifies a second particular storage device in a second particular set of storage devices in the plurality of storage devices which is suitable for appropriation from the second particular set, migrates the data set stored in the first particular storage device to the second particular storage deceive and identifies the second particular storage device as a member of the first particular set.