Snapshot Coordination

• US 20140059298A1
• 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
• Granted Patent: US 9,189,396 B2
• Time in Patent Office: Days
• US Class Current: 711/135
• 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 11/203 using migration
• CPC Class Codes: G06F 11/2035 without idle spare hardware
• CPC Class Codes: G06F 11/2046 where the redundant components share persistent storage G06F11/2043 takes precedence
• CPC Class Codes: G06F 12/08 in hierarchically structured memory systems, e.g. virtual memory systems
• CPC Class Codes: G06F 2201/82 Solving problems relating to consistency ensuring consistency in mirrored systems G06F11/2064
• CPC Class Codes: G06F 2201/84 Using snapshots, i.e. a logical point-in-time copy of the data
• CPC Class Codes: G06F 3/06 Digital input from, or digital output to, record carriers , e.g. RAID, emulated record carriers or networked record carriers
• CPC Class Codes: G06F 3/061 Improving I/O performance
• 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 to prepare a volume of the host cache for creating a snapshot of a cached logical unit number (LUN), the request indicating that a snapshot of the cached LUN will be taken, preparing, in response to the first request, the volume of the host cache for creating the snapshot of the cached LUN depending on a mode of the host cache, receiving, at the host cache, a second request to create the snapshot of the cached LUN, and in response to the second request, creating, at the host cache, the snapshot of the cached LUN.

Claims

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

receiving at a host cache, a first request to prepare a volume of the host cache for creating a snapshot of a cached logical unit number (LUN), the request indicating that a snapshot of the cached LUN will be taken;

preparing, in response to the first request, the volume of the host cache for creating the snapshot of the cached LUN depending on a mode of the host cache;

receiving, at the host cache, a second request to create the snapshot of the cached LUN; and

in response to the second request, creating, at the host cache, the snapshot of the cached LUN.

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

3. The method of claim 1, further comprising receiving a third request to cancel creating the snapshot when preparing the volume for creating the snapshot of the cached LUN and creating the snapshot of the cached LUN exceeds a set amount of time.

4. The method of claim 1, wherein the mode of the host cache comprises at least one of write-through (WT), write-back (WB), or write-back-write-through (WB-WT) switching.

5. The method of claim 4, wherein preparing the volume for creating the snapshot of the cached LUN comprises:

flushing a set of data comprising at least one snapshot of the cached LUN when the host cache is in WB or WB-WT switching modes;

switching the host cache to WT mode when the host cache is in WT-WB switching mode; and

sending a message indicating that the volume is prepared for creating the snapshot of the cached LUN.

6. The method of claim 1, wherein creating the snapshot of the cached LUN comprises:

holding the input/output (I/O) during the creation of the snapshot;

when one or more applications are running, holding the data associated with each of the one or more applications that are running; and

generating the snapshot of the cached LUN.

7. The method of claim 1, further comprising storing at the host cache, the snapshot of the cached LUN when the host cache is in a full time write-back mode.

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 to prepare a volume of the host cache for creating a snapshot of a cached logical unit number (LUN), the request indicating that a snapshot of the cached LUN will be taken;

prepare, in response to the first request, the volume of the host cache for creating the snapshot of the cached LUN depending on a mode of the host cache;

receive, at the host cache, a second request to create the snapshot of the cached LUN; and

in response to the second request, create, at the host cache, the snapshot of the cached LUN.

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

10. The system of claim 8, further comprising receive a third request to cancel creating the snapshot when preparing the volume for creating the snapshot of the cached LUN and creating the snapshot of the cached LUN exceeds a set amount of time.

11. The system of claim 8, wherein the mode of the host cache comprises at least one of write-through (WT), write-back (WB), or write-back-write-through (WB-WT) switching.

12. The system of claim 11, wherein prepare the volume for creating the snapshot of the cached LUN comprises:

flush a set of data comprising at least one snapshot of the cached LUN when the host cache is in WB or WB-WT switching modes;

switch the host cache to WT mode when the host cache is in WT-WB switching mode; and

send a message indicating that the volume is prepared for creating the snapshot of the cached LUN.

13. The system of claim 8, wherein create the snapshot of the cached LUN comprises:

hold the input/output (I/O) during the creation of the snapshot;

when one or more applications are running, hold the data associated with each of the one or more applications that are running; and

generate the snapshot of the cached LUN.

14. The system of claim 8, further comprising store at the host cache, the snapshot of the cached LUN when the host cache is in a full time write-back mode.

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 to prepare a volume of the host cache for creating a snapshot of a cached logical unit number (LUN), the request indicating that a snapshot of the cached LUN will be taken;

prepare, in response to the first request, the volume of the host cache for creating the snapshot of the cached LUN depending on a mode of the host cache;

receive, at the host cache, a second request to create the snapshot of the cached LUN; and

in response to the second request, create, at the host cache, the snapshot of the cached LUN.

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

17. The media of claim 15, further comprising receive a third request to cancel creating the snapshot when preparing the volume for creating the snapshot of the cached LUN and creating the snapshot of the cached LUN exceeds a set amount of time.

18. The media of claim 15, wherein the mode of the host cache comprises at least one of write-through (WT), write-back (WB), or write-back-write-through (WB-WT) switching.

19. The media of claim 18, wherein prepare the volume for creating the snapshot of the cached LUN comprises:

flush a set of data comprising at least one snapshot of the cached LUN when the host cache is in WB or WB-WT switching modes;

switch the host cache to WT mode when the host cache is in WT-WB switching mode; and

send a message indicating that the volume is prepared for creating the snapshot of the cached LUN.

20. The media of claim 15, wherein create the snapshot of the cached LUN comprises:

hold the input/output (I/O) during the creation of the snapshot;

when one or more applications are running, hold the data associated with each of the one or more applications that are running; and

generate the snapshot of the cached LUN.