Alternate Storage Arrangement in a Distributed Data Storage System with Key-Based Addressing

• US 20160054939A1
• Filed: 12/12/2014
• Published: 02/25/2016
• Est. Priority Date: 08/21/2014
• Status: Active Grant

• Current Assignee: VMware, Inc. (Broadcom, Inc.), Vmware LLC (Broadcom, Inc.)
• Original Assignee: Datrium, Inc. (Broadcom, Inc.)
• Inventors: WANG, Zhe III, PATTERSON, R. Hugo, HUANG, Mark L.
• Granted Patent: US 10,514,982 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 2211/1061 Parity-single bit-RAID4, i.e. RAID 4 implementations

Abstract

In a Distributed Virtual Array data storage system, data chunks making up data containers and identified by keys, which are independent of physical storage locations, are written in storage devices according to layouts specified in a layout data structure. When any of the storage devices becomes inaccessible, the chunks nominally designated to be written in the inaccessible storage devices are instead written to alternate devices. Information indicating writing to an alternate device may be included in or along with such chunks so as to make them easily identifiable during later reconstruction or re-writing to the intended storage device when it again becomes available.

Claims

1. A method for writing data to a plurality of storage devices,

said data being grouped as containers written by at least one writing entity within a corresponding one of a plurality of hosts, each container being identified by a unique key that is independent of physical storage identifiers and comprising a set of data chunks nominally designated for writing to different ones of the plurality of storage devices according to a layout pattern, said method comprising:

detecting inaccessibility of one of the plurality of storage devices in which data chunks are to be written; and

for each container having a data chunk nominally designated for writing to the inaccessible storage device, writing the data chunk to an alternate one of the storage devices.

2. The method of claim 1, further comprising:

compiling the layouts into a layout data structure; and

including, in the layout data structure, alternate storage assignments, each alternate storage assignment specifying, per layout, in which of the storage devices data chunks stored in the inaccessible storage are to be written.

3. The method of claim 2, further comprising distributing to the hosts the layout data structure, including the alternate storage assignments.

4. The method of claim 1, further comprising associating with each chunk written to an alternate storage device information indicating that it has been written to the alternate storage.

5. The method of claim 4, in which the information associated with each chunk written to an alternate storage device indicating that is has been so written is metadata associated with each such chunk.

6. The method of claim 4, in which the information associated with each chunk written to an alternate storage device indicating that is has been so written is an indication added into the key associated with each such chunk.

7. The method of claim 4, further comprising including, in each key, information indicating according to which layout the corresponding container is stored.

8. The method of claim 1, further comprising moving a chunk written in an alternate storage device to the storage device in which it is nominally designated to be written to according to the layout pattern when the nominally designated storage device again becomes accessible.

9. The method of claim 1, further comprising:

computing and associating with each set of data chunks at least one correction chunk; and

when a chunk written in its nominally designated storage device becomes inaccessible, reconstructing said chunk from the remaining chunks in the set, including the at least one correction chunk and the chunk in the alternate storage device.

10. The method of claim 9, further comprising:

including, in each set of data chunks, reconstruction information sufficient to reconstruct a plurality of unavailable data chunks;

for layout patterns in which a plurality of storage devices have become inaccessible at the same time, reconstructing, from the remaining chunks in each set and the reconstruction information, data sets stored in the respective layout patterns in an order such the data sets stored according to layout patterns having relatively more unavailable data chunks are reconstructed before data sets in layout patterns having relatively fewer unavailable data chunks.

11. The method of claim 10, in which the reconstruction information is a plurality of correction chunks.

24. The system of claim 1, in which:

the layouts are compiled into a layout data structure; and

alternate storage assignments are included in the layout data structure, each alternate storage assignment specifying, per layout, in which of the storage devices data chunks stored in the inaccessible storage are to be written.

25. The system of claim 1, in which the at least one management component is further configured for moving a chunk written in an alternate storage device to the storage device in which it is nominally designated to be written to according to the layout pattern when the nominally designated storage device again becomes accessible.

12. A computer program product comprising code embodied in a non-transitory storage medium, said code being executable on at least one processor causing the processor(s) for writing data from at least one client to a plurality of storage devices, said data being grouped as containers written by at least one writing entity within a corresponding one of a plurality of hosts, each container being identified by a unique key that is independent of physical storage identifiers and comprising a set of data chunks nominally designated for writing to different ones of the plurality of storage devices according to a layout pattern, said code further causing the processor(s):

to detect inaccessibility of one of the plurality of storage devices in which data chunks are to be written; and

for each container having a data chunk nominally designated for writing to the inaccessible storage device, to write the data chunk to an alternate one of the storage devices.

13. The computer program product of claim 12, further comprising code causing the processor(s):

to compile the layouts into a layout data structure; and

to include, in the layout data structure, alternate storage assignments, each alternate storage assignment specifying, per layout, in which of the storage devices data chunks stored in the inaccessible storage are to be written.

14. The computer program product of claim 13, further comprising code causing the processor(s) to distribute to the hosts the layout data structure, including the alternate storage assignments.

15. The computer program product of claim 12, further comprising code causing the processor(s) to associate with each chunk written to an alternate storage device information indicating that it has been written to the alternate storage.

16. The computer program product of claim 15, in which the information associated with each chunk written to an alternate storage device indicating that is has been so written is metadata associated with each such chunk.

17. The computer program product of claim 15, in which the information associated with each chunk written to an alternate storage device indicating that is has been so written is an indication added into the key associated with each such chunk.

18. The computer program product of claim 15, further comprising code causing the processor(s) to include, in each key, information indicating according to which layout the corresponding container is stored.

19. The computer program product of claim 12, further comprising code causing the processor(s) to move a chunk written in an alternate storage device to the storage device in which it is nominally designated to be written to according to the layout pattern when the nominally designated storage device again becomes accessible.

20. The computer program product of claim 12, further comprising code causing the processor(s):

to compute and associate with each set of data chunks at least one correction chunk; and

when a chunk written in its nominally designated storage device becomes inaccessible, to reconstruct said chunk from the remaining chunks in the set, including the at least one correction chunk and the chunk in the alternate storage device.

21. The computer program product of claim 12, further comprising code causing the processor(s):

to include, in each set of data chunks, reconstruction information sufficient to reconstruct a plurality of unavailable data chunks;

for layout patterns in which a plurality of storage devices have become inaccessible at the same time, to reconstruct, from the remaining chunks in each set and the reconstruction information, data sets stored in the respective layout patterns in an order such the data sets stored according to layout patterns having relatively more unavailable data chunks are reconstructed before data sets in layout patterns having relatively fewer unavailable data chunks.

22. The computer program product of claim 21, in which the reconstruction information is a plurality of correction chunks.

23. A data storage system comprising:

a plurality of storage devices to which data is written by at least one writing entity within a corresponding one of a plurality of hosts, said data being grouped as containers, each container being identified by a unique key that is independent of physical storage identifiers and comprising a set of data chunks nominally designated for writing to different ones of the plurality of storage devices according to a layout pattern;

at least one management component configured for detecting inaccessibility of one of the plurality of storage devices in which data chunks are to be written; and

for each container having a data chunk nominally designated for writing to the inaccessible storage device, writing the data chunk to an alternate one of the storage devices.