Mirrored cache protection
View Patent ↗Methods of protecting cache data are provided. For example, various methods are described that assist in handling dirty write data cached in memory by duplication into other locations to protect against data loss. One method includes caching a data item from a data source in a first cache device. The data item cached in the first cache device is designated with a first designation. In response to the data item being modified by a data consumer, the designation of the data item in the first cache device is re-assigned from the first designation to a second designation, and the data item with the second designation is copied to a second cache device.
1. A method of cache data redundancy, comprising:
providing a plurality of cache devices, wherein each of the plurality of cache devices is partitioned into a first allocated area and a second allocated area, the first allocated area being used for storing data items that are in an unmodified form and the second allocated area being used for storing data items that are in a modified form;
copying a data item from a data source to the first allocated area in one of the plurality of cache devices, the data item being in the unmodified form;
in response to the data item being modified by a data consumer,
(a) logically removing the data item from the first allocated area of one of the plurality of cache devices;
(b) copying the data item in the modified form to the second allocated area in one of the plurality of cache devices; and
transferring the data item in the modified form from the second allocated area of one of the plurality of cache devices to the data source, in response to the transferring to the data source, copying the data item in the modified form from the second allocated area of the one of the plurality of cache devices to the first allocated area of one of the plurality of cache devices.
2. The method of cache data redundancy of claim 1 further comprising:
in response to transferring the data item in the modified form to the data source,
logically removing the data item in the modified form from the second allocated area of the plurality of cache devices.
3. The method of cache data redundancy of claim 1 , further comprising:
protecting the data item in the modified form stored in the second allocated area through a data striping protection scheme.
4. The method of cache data redundancy of claim 1 further comprising:
dynamically allocating a size of the first and second allocated areas.
5. The method of cache data redundancy of claim 1 further comprising:
selecting one of the plurality of cache devices for copying the data item based on a load balancing algorithm.
6. The method of cache data redundancy of claim 1 further comprising:
associating location data with the data item in the unmodified form stored in the first allocated area.
7. A method of protecting cache data, comprising:
caching a data item from a data source in a first cache device;
designating the data item in the first cache device with a first designation;
in response to the data item being modified by a data consumer, re-assigning the designation of the data item in the first cache device from the first designation to a second designation; and
copying the data item with the second designation to a second cache device, wherein the first designation used to associate state information related to an unmodified form of the data item and the second designation used to associate state information related to a modified form of the data item, in response to the copying, re-initializing the data item in the first cache device, the re-initializing changing the designation of the data item from the second designation to the first designation.
8. The method of protecting cache data of claim 7 , further comprising:
transferring the data item with the second designation from the second cache device to the data source, the transferring causes re-initializing of the designation of the data item, the re-initializing changing the designation of the data item with the second designation in the second cache device to the first designation.
9. The method of protecting cache data of claim 7 , further comprising:
receiving the data item from the data source.
10. The method of protecting cache data of claim 7 , further comprising:
transferring the data item with the first designation to the data consumer.
11. The method of protecting cache data of claim 7 , further comprising:
receiving the data item in a modified form from the data consumer.
12. The method of protecting cache data of claim 7 , further comprising:
transferring the data item with the second designation to a third cache device.
13. The method of protecting cache data of claim 7 , wherein the data item includes state information indicating the data item is in the modified form.
14. A system for protecting cache data comprising:
a data source operable to store a data item;
a data consumer operable to request the data item stored in the data source, the data consumer further operable to modify the data item; and
a plurality of cache devices, each of the plurality of cache devices partitioned into a first allocated area and a second allocated area, the plurality of cache devices including,
a first cache device operable to copy the data item stored in the data source into the first allocated area that is used for storing data in unmodified form, and designate the data item in an unmodified state with a first designation, the first cache device further operable to modify the designation of the data item in a modified state to a second designation in response to the data item being modified by the data consumer; and
a second cache device operable to store the copy of the data item with the second designation in the second allocation area that is used for storing data in modified form, wherein the first designation is used to associate state information related to an unmodified form of the data item and the second designation is used to associate state information related to a modified form of the data item and wherein the second cache device is further operable to transfer the data item in the modified form to the data source and to copy the data item in the modified form from the second allocated area to the first allocated area of any one of the plurality of cache devices, the copying causes re-initializing of the data item from second designation to the first designation in the first allocated area.
15. The system for protecting cache data of claim 14 , the plurality of cache devices further comprising:
a third cache device operable to store the copy of the data item with the second designation from the first cache device in the corresponding second allocation area of the third cache device.
16. The system for protecting cache data of claim 14 , wherein the first cache device is further operable to logically remove the data item stored in the first cache in response to the data item being modified by the data consumer.
17. The system for protecting cache data of claim 14 , wherein the data source is further operable to receive the copy of the data item with the second designation from the second cache device.
18. The system for protecting cache data of claim 14 , wherein each of the plurality of cache devices are separate.
19. The system for protecting cache data of claim 14 , wherein the first and second cache devices have different storage capacities.
20. The system for protecting cache data of claim 14 , wherein the data source is further operable to generate the data item.