Snapshot Access

• US 20140059300A1
• Filed: 08/24/2012
• Published: 02/27/2014
• Est. Priority Date: 08/24/2012
• Status: Active Grant

• Current Assignee: Dell Products BV (Dell Technologies Inc.)
• Original Assignee: Dell Products LP (Dell Technologies Inc.)
• Inventors: Olin, Marc David, Klemm, Michael James, Pandit, Ranjit
• Granted Patent: US 9,262,329 B2
• Time in Patent Office: Days
• US Class Current: 711/142
• CPC Class Codes: G06F 11/00 Error detection; Error correction; Monitoring error detection, correction or monitoring in information storage based on relative movement between record carrier and transducer G11B20/18; monitoring, i.e. supervising the progress of recording or reproducing G11B27/36; in static stores G11C29/00
• CPC Class Codes: G06F 11/2046 where the redundant components share persistent storage G06F11/2043 takes precedence
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 12/16 Protection against loss of memory contents contains no material, see G06F11/00
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]

Abstract

In one embodiment, a method performed by one or more computing devices includes receiving at a host cache a first request for data comprising at least one snapshot of a cached logical unit number (LUN), sending, by the host cache, the data comprising at least one snapshot of the cached LUN in response to the first request, and in response to the completing sending the data comprising at least one snapshot of the cached LUN, sending, by the host cache, a first response indicating that sending the data is complete.

Claims

1. A method, performed by one or more computing devices, comprising:

receiving at a host cache a first request for data comprising at least one snapshot of a cached logical unit number (LUN);

sending, by the host cache, the data comprising at least one snapshot of the cached LUN in response to the first request; and

in response to the completing sending the data comprising at least one snapshot of the cached LUN, sending, by the host cache, a first response indicating that sending the data is complete.

2. The method of claim 1, wherein the at least one snapshot of the cached LUN comprises a data map of the cached LUN that indicates which data blocks are associated with which files.

3. The method of claim 2, wherein the data comprising at least one snapshot of the cached LUN comprises a first snapshot or the cached LUN and a second snapshot of the cached LUN, and in response to the first request, sending, by the host cache, the data comprising the first snapshot of the cached LUN and then the data comprising the second snapshot of the cached LUN.

4. The method of claim 1, further comprising, in response to sending, by the host cache, the data comprising at least one snapshot of a cached LUN being incomplete, sending, by the host cache, a second response that cancels sending the data.

5. The method of claim 1, further comprising deleting, at the host cache, the data comprising the at least one snapshot.

6. The method of claim 1, further comprising, switching, by the host cache, from a first mode to a second mode, in response to completing the sending of the data comprising at least one snapshot of the cached LUN.

7. The method of claim 6, wherein the first mode and the second mode of the host cache comprises at least one of write-through (WT), write-back (WB), or write-back-write-through (WB-WT) switching.

8. A system comprising:

a memory comprising instructions executable by one or more processors; and

the one or more processors coupled to the memory and operable to execute the instructions, the one or more processors being operable when executing the instructions to;

receive at a host cache a first request for data comprising at least one snapshot of a cached logical unit number (LUN);

send, by the host cache, the data comprising at least one snapshot of the cached LUN in response to the first request; and

in response to the completing sending the data comprising at least one snapshot of the cached LUN, send, by the host cache, a first response indicating that sending the data is complete.

9. The system of claim 8, wherein the at least one snapshot of the cached LUN comprises a data map of the cached LUN that indicates which data blocks are associated with which files.

10. The system of claim 9, wherein the data comprising at least one snapshot of the cached LUN comprises a first snapshot or the cached LUN and a second snapshot of the cached LUN, and in response to the first request, send, by the host cache, the data comprising the first snapshot of the cached LUN and then the data comprising the second snapshot of the cached LUN.

11. The system of claim 8, further comprising, in response to sending, by the host cache, the data comprising at least one snapshot of a cached LUN being incomplete, send, by the host cache, a second response that cancels sending the data.

12. The system of claim 8, further comprising delete, at the host cache, the data comprising the at least one snapshot.

13. The system of claim 8, further comprising, switch, by the host cache, from a first mode to a second mode, in response to completing the sending of the data comprising at least one snapshot of the cached LUN.

14. The method of claim 13, wherein the first mode and the second mode of the host cache comprises at least one of write-through (WT), write-back (WB), or write-back-write-through (WB-WT) switching.

15. One or more computer-readable non-transitory storage media embodying software operable when executed by one or more computer systems to:

receive at a host cache a first request for data comprising at least one snapshot of a cached logical unit number (LUN);

send, by the host cache, the data comprising at least one snapshot of the cached LUN in response to the first request; and

in response to the completing sending the data comprising at least one snapshot of the cached LUN, send, by the host cache, a first response indicating that sending the data is complete.

16. The media of claim 15, wherein the at least one snapshot of the cached LUN comprises a data map of the cached LUN that indicates which data blocks are associated with which files.

17. The media of claim 16, wherein the data comprising at least one snapshot of the cached LUN comprises a first snapshot or the cached LUN and a second snapshot of the cached LUN, and in response to the first request, send, by the host cache, the data comprising the first snapshot of the cached LUN and then the data comprising the second snapshot of the cached LUN.

18. The media of claim 15, further comprising, in response to sending, by the host cache, the data comprising at least one snapshot of a cached LUN being incomplete, send, by the host cache, a second response that cancels sending the data.

19. The media of claim 15, further comprising delete, at the host cache, the data comprising the at least one snapshot.

20. The media of claim 15, further comprising, switch, by the host cache, from a first mode to a second mode, in response to completing the sending of the data comprising at least one snapshot of the cached LUN, the first mode and the second mode of the host cache comprises at least one of write-through (WT), write-back (WB), or write-back-write-through (WB-WT) switching.