System and method for managing data in a distributed system

• US 7,058,773 B1
• Filed: 01/16/2003
• Issued: 06/06/2006
• Est. Priority Date: 01/16/2003
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Mackie, Robert A., Schomburg, Keith R., Bakita, Thomas R., Frye, Dwight R. Jr., White, John G.
• Primary Examiner(s): Nguyen, Hiep T.
• Application Number:
  US10/346,352
• Time in Patent Office: 1,237 Days
• Field of Search: 711/156, 711/162, 711/161, 707/204, 707/103.R, 707/203, 714/6
• US Class Current: 711/162
• CPC Class Codes: G06F 11/1666 where the redundant component is memory or memory area

Abstract

A memory system includes a client device and multiple memory devices. The client device communicates an operation request pertaining to a particular data object to one memory device. Referencing a host table, the memory device identifies multiple memory devices associated with an object key of the data object. The memory device communicates the operation request to the identified memory devices to be completed. If one of the memory devices in the memory system becomes inaccessible, the memory system is capable of replacing the inaccessible memory device in the host table. Furthermore, if a new memory device is added to the memory system, the memory system is capable of modifying the host table to associate some of the possible object keys with the new memory device.

Claims

1. A method for managing data in a distributed system comprising:

identifying a first memory device and a second memory device from a plurality of memory devices, wherein the first memory device and the second memory are associated with a data object;

storing the data object on the first memory device and the second memory device;

determining that one of the first memory device and the second memory device has become inaccessible;

identifying, in response to determining that one of the first memory device and the second memory device has become inaccessible, a selected one of the first memory device and the second memory device that remains accessible;

associating a third memory device with the data object in response to determining that one of the first memory device and the second memory device has become inaccessible; and

copying the data object from the selected memory device to on the third memory device.

2. The method of claim 1, wherein identifying the first memory device and the second memory device comprises:

reading a first value and a second value associated with the data object in a hash table, wherein the first value identifies the first memory device and the second value identifies the second memory device.

3. The method of claim 1, further comprising disassociating the first memory device from the data object in response to determining that the first memory device has become inaccessible.

4. The method of claim 1, further comprising:

determining that a fourth memory device has become accessible.

5. The method of claim 4, further comprising:

reading a first value and a second value associated with a second data object in a hash table, wherein the first value identifies the second memory device and the second value identifies the third memory device; and

associating a third value with the second data object in the hash table in response to determining the fourth memory device has become accessible, wherein the third value identifies the fourth memory device.

6. The method of claim 4, further comprising:

storing the identity of the second memory device; and

referencing the stored identity of the second memory device to access a stored data object that was stored prior to the fourth memory device becoming accessible.

7. The method of claim 1, wherein the data object comprises transient information.

8. A data management system comprising:

a plurality of memory devices comprising;

a first memory device operable to store a data object;

a second memory device operable to store the data object; and

a third memory device operable to store the data object in response to a change in status of one of the plurality of memory devices; and

a processor operable to;

determine that one of the first memory device and the second memory device has become inaccessible;

identify, in response to determining that one of the first memory device and the second memory device has become inaccessible, a selected one of the first memory device and the second memory device that remains accessible; and

copy the data object from the selected memory device to the third memory device; and

a host table operable to associate the data object with the first memory device and with the second memory device and to associate the data object with the third memory device in response to one of the first memory device and the second memory device becoming inaccessible.

9. The system of claim 8, herein each memory device is operable to:

identify, based on the host table, memory devices that are associated with a first data object in response to a first delete request specifying the first data object;

transmit the delete request to the identified memory devices; and

delete a second data object in response to a second delete request received from another memory device.

10. The system of claim 8, wherein:

the host table is operable to disassociate the first memory device from the data object in response to the first memory device becoming inaccessible.

11. The system of claim 8, further comprising a fourth memory device and a second data object, wherein the second data object is associated with the second memory device and the third memory device, and wherein at least one of the memory devices is operable to associate the fourth memory device with the second data object in response to the fourth memory device becoming accessible.

12. The system of claim 11, wherein:

the host table is operable to store the identity of the second memory device and at least one of the memory devices is operable to retrieve the identity of the second memory device in order to access a data object stored before the fourth memory device became accessible.

13. The system of claim 8, wherein the plurality of memory devices are operable to:

receive an object key associated with a data object;

hash the object key to create a hash value; and

use the value to identify the first memory device and second memory device associated with the data object in the host table.

14. The system of claim 8, wherein the data object comprises transient data.

15. An apparatus for managing data, comprising:

a processor operable to;

determine that one of a first memory device and a second memory device has become inaccessible;

identify, in response to determining that one of the first memory device and the second memory device has become inaccessible, a selected one of the first memory device and the second memory device that remains accessible; and

copy a data object from the selected memory device to a third memory device; and

a host table operable to associate the data object with the first memory device and with the second memory device and operable to associate the data object with the third memory device in response to one of the first memory device and the second memory device becoming inaccessible.

16. The apparatus of claim 15, wherein:

identifying the selected memory device comprises reading at least one of a first value and a second value from a host pair associated with the data object in the host table, wherein the first value identifies the first memory device and the second value identifies the second memory device; and

associating the third memory device comprises adding a third value identifying the third memory device to the host pair associated with the data object in the host table.

17. The apparatus of claim 15, wherein a second data object is associated with the second memory device and the third memory device in the host table, and wherein the host table is operable to associate a fourth memory device with the second data object in response to the fourth memory device becoming accessible.

18. The apparatus of claim 15, wherein the host table is further operable to disassociate the data object from the first memory device in response to the one of the first memory device and the second memory device becoming inaccessible.

19. The apparatus of claim 15, wherein the host table is further operable to:

determine that a fourth memory device has become accessible;

store the identity of a selected one of the second memory device and the third memory device; and

reference the stored identity of the selected memory device to access a stored data object that was stored prior to the fourth memory device becoming accessible.

20. A computer readable medium having code for managing data, the code operable to:

identify a first memory device and a second memory device from a plurality of memory devices, wherein the first memory device and the second memory are associated with a data object;

store the data object on the first memory device and the second memory device;

determine that one of the first memory device and the second memory device has become inaccessible;

identify, in response to one of the first memory device and the second memory device becoming inaccessible, a selected one of the first memory device and the second memory device that remains accessible;

associate a third memory device with the data object in response to determining that one of the first memory device and the second memory device has become inaccessible; and

copy the data object from the selected memory device to en the third memory device.

21. The computer readable medium of claim 20, wherein the code is operable to identify the first memory device and the second memory device by reading a first hash value and a second hash value associated with the data object in a host table, wherein the first hash value identifies a first memory device and the second hash value identifies a second memory device;

and wherein the code is further operable to associate a third hash value with the data object in the host table in response to determining that one of the first memory device and the second memory device has become inaccessible.

22. The computer readable medium of claim 20, wherein the code is further operable to disassociate the inaccessible memory device from the data object in response to determining that the inaccessible memory device has become inaccessible.

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

determine that a fourth memory device has become accessible.

24. The computer readable medium of claim 23, wherein the code is further operable to:

store the identity of a selected one of the second memory device and the third memory device; and

reference the stored identity of the selected memory device to access a stored data object that was stored prior to the fourth memory device becoming accessible.

25. The computer readable medium of claim 23, wherein the code is further operable to:

read a first value and a second value associated with a second data object in a hash table, wherein the first value identifies the second memory device and the second value identifies the third memory device; and

associate a third value with the second data object in the hash table in response to determining the fourth memory device has become accessible, wherein the third value identifies the fourth memory device.

26. The computer readable medium of claim 20, wherein the data object comprises transient information.

27. A system for managing data in a distributed system, comprising:

means for identifying a first memory device and a second memory device from a plurality of memory devices, wherein the first memory device and the second memory are associated with a data object;

means for storing the data object on the first memory device and the second memory device;

means for determining that one of the first memory device and the second memory device has become inaccessible;

means for identifying, in response to determining that one of the first memory device and the second memory device has become inaccessible, a selected one of the first memory device and the second memory device that remains accessible;

means for associating a third memory device with the data object in response to determining that one of the first memory device and the second memory device has become inaccessible; and

means for copying the data object from the selected memory device to the third memory device.

28. The system of claim 27, wherein the means for identifying the first memory device and the second memory device comprises:

means for reading a first hash value and a second hash value associated with the data object in a host table, wherein the first hash value identifies the first memory device and the second hash value identifies the second memory device.

29. The system of claim 27, further comprising:

means for disassociating the inaccessible memory device from the data object in response to determining that the inaccessible memory device has become inaccessible.

30. The system of claim 27, further comprising:

means for determining a fourth memory device has become accessible.

31. The system of claim 30, further comprising:

means for reading a first hash value and a second hash value associated with a second data object in a host table, wherein the first hash value identifies the second memory device and the second hash value identifies the third memory device; and

means for associating a third hash value with the second data object in the host table in response to determining that the fourth memory device has become accessible, wherein the third hash value identifies the fourth memory device.

32. The system of claim 27, further comprising:

means for storing the identity of a selected one of the second memory device and the third memory device; and

means for referencing the stored identity of the selected memory device to access a stored data object that was stored prior to the fourth memory device becoming accessible.

33. The system of claim 27, wherein the data object comprises transient information.