DETERMINING MODIFIED DATA IN CACHE FOR USE DURING A RECOVERY OPERATION

1 . A method, comprising:

detecting an event during which processing of writes to a storage device is suspended;

scanning a cache including modified data not destaged to the storage device to determine the data units having modified data in response to detecting the event;

indicating the data units having the modified data in a backup storage; and

using the indication of the data units having the modified data in the backup storage during a recovery operation.

2 . The method of claim 1 , wherein the detected event comprises a notification of a power failure and wherein the operations of scanning the cache and indicating the data units having the modified data in the backup storage are performed using power from a backup battery power.

3 . The method of claim 1 , further comprising:

writing the indication of the data units having the modified data from the backup storage to the storage device.

4 . The method of claim 1 , wherein the backup storage comprises a non-volatile storage device having a separate battery power source from a system including the cache and the backup storage.

5 . The method of claim 1 , wherein the cache and backup storage comprise a first cache and a first backup storage, and wherein a second backup storage stores writes to the first cache not destaged to the storage device and wherein the first backup storage stores writes to a second cache not destaged to the storage device, wherein the first backup storage includes indication of the data units having the modified data in the first cache.

6 . The method of claim 5 , further comprising:

scanning the second cache including modified data not destaged to the storage device to determine the modified data in response to detecting the event;

indicating the data units having the modified data in the second cache in the first backup storage; and

using the indication of the data units having modified data in the second backup storage during the recovery operation.

7 . The method of claim 6 , further comprising:

initiating an operation to destage the modified data in the first and second backup torages to the storage device during the recovery operation.

8 . The method of claim 6 , further comprising:

using the indication of the data units having the modified data in the second backup storage indicating the modified data in the first cache during the recovery operation.

9 . The method of claim 8 , wherein using the indication of the data units having modified data in the first and second backup storages comprises:

using indication of the data units having modified data in the second cache in the second backup storage during the recovery operation in response to determining that the first backup storage is unavailable to use to recover the modified data in the second cache; and

using indication of the data units having the modified data in the first cache in the first backup storage during the recovery operation in response to determining that the second backup storage is unavailable to use to recover the modified data in the storage cache.

10 . The method of claim 9 , wherein using the indication of the data units having the modified data in the first or the second cache comprises recovering the indication of the data units having the modified data.

11 . A system in communication with a storage device, comprising:

a cache;

a backup storage;

a storage manager in communication with the cache and the backup storage, wherein the storage manager performs operations, the operations comprising:

detecting an event during which processing of writes to the storage device is suspended;

scanning the cache including modified data not destaged to the storage device to determine the data units having modified data in response to detecting the event;

indicating the data units having the modified data in the backup storage; and

using the indication of the data units having the modified data in the backup storage during a recovery operation.

12 . The system of claim 11 , wherein the operations further comprise:

writing the indication of the data units having the modified data from the backup storage to the storage device.

13 . The system of claim 11 , wherein the cache and backup storage comprise a first cache and a first backup storage, further comprising:

a second backup storage storing writes to the first cache not destaged to the storage device;

a second cache, wherein the first backup storage stores writes to the second cache not destaged to the storage device, wherein the first backup storage includes indication of the data units having the modified data in the first cache.

14 . The system of claim 13 , further comprising:

a second storage manager in communication with the second backup storage and the second cache, wherein the second storage manager performs operations, the operations comprising:

scanning the second cache including modified data not destaged to the storage device to determine the modified data in response to detecting the event;

indicating the data units having the modified data in the second cache in the first backup storage; and

using the indication of the data units having modified data in the second backup storage during the recovery operation.

15 . The system of claim 14 , wherein the first and second storage managers further perform:

initiating an operation to destage the modified data in the first and second backup storages to the storage device during the recovery operation.

16 . The system of claim 14 , wherein the second storage manager further performs:

using the indication of the data units having the modified data in the second backup storage indicating the modified data in the first cache during the recovery operation.

17 . The system of claim 16 , wherein using the indication of the data units having modified data in the first and second backup storages comprises:

using indication of the data units having modified data in the second cache in the second backup storage during the recovery operation in response to determining that the first backup storage is unavailable to use to recover the modified data in the second cache; and

using indication of the data units having the modified data in the first cache in the first backup storage during the recovery operation in response to determining that the second backup storage is unavailable to use to recover the modified data in the storage cache.

18 . An article of manufacture implementing a program to communicate with a storage device, a cache, and a backup storage and executed to perform operations, the operations comprising:

detecting an event during which processing of writes to the storage device is suspended;

scanning the cache including modified data not destaged to the storage device to determine the data units having modified data in response to detecting the event;

indicating the data units having the modified data in the backup storage; and

using the indication of the data units having the modified data in the backup storage during a recovery operation.

19 . The article of manufacture of claim 18 , further comprising:

writing the indication of the data units having the modified data from the backup storage to the storage device.

20 . The article of manufacture of claim 18 , wherein the cache and backup storage comprise a first cache and a first backup storage, and wherein a second backup storage stores writes to the first cache not destaged to the storage device and wherein the first backup storage stores writes to a second cache not destaged to the storage device, wherein the first backup storage includes indication of the data units having the modified data in the first cache, wherein the program comprises a first program and wherein the article of manufacture further includes a second program that performs operations with respect to the second cache and the second backup storage.

21 . The article of manufacture of claim 20 , wherein the second program operations further comprise:

scanning the second cache including modified data not destaged to the storage device to determine the modified data in response to detecting the event;

indicating the data units having the modified data in the second cache in the first backup storage; and

using the indication of the data units having modified data in the second backup storage during the recovery operation.

22 . The article of manufacture of claim 21 , wherein the operations further comprise:

initiating an operation to destage the modified data in the first and second backup storages to the storage device during the recovery operation.

23 . The article of manufacture of claim 21 , wherein the second program operations further comprise:

using the indication of the data units having the modified data in the second backup storage indicating the modified data in the first cache during the recovery operation.

24 . The article of manufacture of claim 23 , wherein using the indication of the data units having modified data in the first and second backup storages comprises:

using indication of the data units having modified data in the second cache in the second backup storage during the recovery operation in response to determining that the first backup storage is unavailable to use to recover the modified data in the second cache; and

using indication of the data units having the modified data in the first cache in the first backup storage during the recovery operation in response to determining that the second backup storage is unavailable to use to recover the modified data in the storage cache.

25 . The article of manufacture of claim 24 , wherein using the indication of the data units having the modified data in the first or the second cache comprises recovering the indication of the data units having the modified data.