Data tracking for efficient recovery of a storage array

Patent metadata

Field	Value
Publication number	US-9547552-B2
Application number	US-201414567743-A
Country	US
Kind code	B2
Filing date	Dec 11, 2014
Priority date	Dec 11, 2014
Publication date	Jan 17, 2017
Grant date	Jan 17, 2017

Abstract

A system and method for maintaining operation of a storage array with one or more failed storage devices and for quickly recovering when failing devices are replaced are provided. In some embodiments, the method includes receiving a data transaction directed to a volume and determining that a storage device associated with the volume is inoperable. In response to determining that the storage device is inoperable, a data extent is recorded in a change log in a storage controller cache. The data extent is associated with the data transaction and allocated to the storage device that is inoperable. The data transaction is performed using at least one other storage device associated with the volume, and data allocated to the storage device is subsequently reconstructed using the recorded data extent.

First claim

What is claimed is:

1. A method comprising:
receiving a data transaction directed to a volume comprising a plurality of storage devices;
determining that a storage device of the plurality of storage devices is inoperable;
in response to determining that the storage device is inoperable, recording, in a change log, a data extent that comprises an address range allocated to the inoperable storage device and data that is to be stored at the address range as a result of the data transaction;
performing the data transaction using at least one other storage device of the plurality of storage devices; and
subsequently reconstructing data allocated to the storage device using the recorded data extent.

2. The method of claim 1 , further comprising:
recognizing a replacement storage device of the volume; and
determining that the replacement storage device corresponds to the storage device that is inoperable, and
wherein the reconstructing of the data further comprises includes storing the reconstructed data to the replacement storage device.

3. The method of claim 2 , wherein determining that the replacement storage device corresponds to the storage device that is inoperable further comprises:
comparing a device identifier of the replacement storage device to a device identifier of the storage device that is inoperable.

4. The method of claim 2 , wherein determining that the replacement storage device corresponds to the storage device that is inoperable further comprises:
verifying that a data set of the replacement storage device corresponds to a data set of the storage device that is inoperable.

5. The method of claim 1 , wherein the change log is stored in a first storage controller cache, and the method further comprises:
maintaining a mirror copy of the change log in a second storage controller cache.

6. The method of claim 5 , wherein maintaining the mirror copy further comprises:
providing a copy of a changed portion of the change log via an inter-controller bus for storing in the second storage controller cache.

7. The method of claim 1 , wherein the data transaction is a first data transaction and wherein the reconstructing of the data allocated to the storage device includes storing the reconstructed data to a replacement storage device, the method further comprising:
receiving a second data transaction during the reconstructing of the data;
determining, using the change log, whether the second data transaction is directed to data that has not been reconstructed; and
based on the determining, performing the second data transaction using the replacement storage device during the reconstructing.

8. The method of claim 1 , wherein the change log comprises a plurality of data extents that correspond to a plurality of address ranges allocated in the inoperable storage device, one address range per data extent.

9. The method of claim 1 , further comprising:
recording, in the change log an indication that the data at the address range of the data extent has been modified by the data transaction.

10. A non-transitory machine-readable medium that has stored thereupon instructions for performing a method of data management, including machine executable code, which when executed by at least one machine, causes the machine to:
receive a data transaction;
determine whether a storage device associated with the data transaction is unable to perform the data transaction;
upon the determination that the storage device associated with the data transaction is unable to perform the data transaction, initialize a log that records modified data extents that comprise address ranges allocated to the storage device and data that is to be stored at the address ranges as a result of the data transaction;
perform the data transaction using at least one other storage device; and
record a data extent modified by the data transaction in the log.

11. The non-transitory machine-readable medium of claim 10 , wherein the machine executable code further causes the machine to:
identify a replacement storage device;
determine whether the replacement storage device corresponds to the storage device that is unable to perform the data transaction; and
based upon the determination that the replacement storage device corresponds to the storage device, selectively reconstruct a portion of a dataset based on the log.

12. The non-transitory machine-readable medium of claim 11 , wherein the machine executable code that causes the machine to selectively reconstruct the portion of the dataset, further comprises machine executable code that causes the machine to:
match data stored on the replacement storage device with data stored on the storage device that is unable to perform the data transaction.

13. The non-transitory machine-readable medium of claim 11 , wherein the machine executable code that causes the machine to selectively reconstruct the portion of the dataset further comprises machine executable code that causes the machine to:
correspond an identifier of the replacement storage device to an identifier of the storage device that is unable to perform the data transaction.

14. The non-transitory machine-readable medium of claim 11 , wherein the data transaction is a first data transaction and wherein the machine executable code further causes the machine to:
receive a second data transaction during the selective reconstruction; and
based on a determination that the second transaction is directed to a reconstructed portion of the dataset, perform the second transaction using the replacement storage device during the selective reconstruction.

15. The non-transitory machine-readable medium of claim 11 , wherein the data transaction is a first data transaction and wherein the machine executable code further causes the machine to:
receive a second data transaction during the selective reconstruction; and
based on a determination that the second transaction is directed to a portion of the dataset that has not been reconstructed:
perform the second data transaction using the at least one other storage device; and
record a data extent modified by the second data transaction in the log.

16. A computing device comprising:
a storage controller in communication with at least one storage device and configured to:
identify a transaction directed to a volume;
determine that a first storage device of a plurality of storage devices associated with the volume is inoperable to perform the transaction; and
based on the determination:
record, in a log an address allocated to the first storage device and data that is to be stored at the address and that has been modified by the transaction;
perform the transaction using a second storage device of the plurality of storage devices associated with the volume;
use the recorded address to identify the data to be stored in a third storage device; and
store the identified data in a third storage device.

17. The computing device of claim 16 , wherein the storage controller is further configured to initialize the log in a storage controller cache based on the determination that the first storage device is inoperable to perform the transaction.

18. The computing device of claim 16 , wherein the storage controller is further configured to:
determine that a dataset of the third storage device corresponds to a dataset of the first storage device; and
identify, using the recorded address, the data to be stored in the third storage device.

19. The computing device of claim 16 , wherein the

Assignees

• Netapp Inc

Inventors

• Segura Theresa L
• Sun Wei
• Parrish Martin
• Humlicek Donald R

Classifications

• G06F11/1088 Primary

  Reconstruction on already foreseen single or plurality of spare disks · CPC title

• G06F11/2069

  Management of state, configuration or failover · CPC title

• G06F11/2058

  using more than 2 mirrored copies · CPC title

• G06F2211/1009

  Cache, i.e. caches used in RAID system with parity · CPC title

• G06F11/2089

  Redundant storage control functionality · CPC title