Storage system snapshot assisted by SSD technology

• US 20100153620A1
• Filed: 12/17/2008
• Published: 06/17/2010
• Est. Priority Date: 12/17/2008
• Status: Active Grant

• Current Assignee: NetApp, Inc.
• Original Assignee: NetApp, Inc.
• Inventors: Dietterich, John, Werning, Jeffrey S., Weber, Bret S., McKean, Brian, El-Batal, Mohamad, Hoglund, Timothy E.
• Granted Patent: US 8,200,922 B2
• Time in Patent Office: Days
• US Class Current: 711/103
• CPC Class Codes: G06F 11/1466 to make the backup process non-disruptive
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/7201 Logical to physical mapping or translation of blocks or pages

Abstract

A method and apparatus for taking a snapshot of a storage system employing a solid state disk (SSD). A plurality of mapping tables in the SSD store data needed to create a one or more point in time snapshots and a current view of the SSD. In response to a write command, the SSD executes its normal write process and updates its mapping tables to indicate the current view of the SSD and additionally retains the original data in a table of pointers to the original data, as the snapshot of an earlier state of the SSD. In the preferred embodiment, the innate ability of SSDs to write data to a new location is used to perform a point-in-time copy with little or no loss in performance in performing the snapshot.

Claims

1. A system for taking a snapshot of a storage device comprising:

a storage device comprising, a first mapping table for address translation, holding data prior to a write action by the storage device, and a second mapping table for address translation, holding data after a write action by the storage device;

wherein the storage device is capable of a point in time copy of the storage device via the data held by the first and second mapping tables.

2. The invention according to claim 1, wherein:

the storage device is a solid state disk (SSD);

the first mapping table holding data relating to a snapshot of the SSD, and the second mapping table holding data relating to current view of the SSD, wherein the SSD uses the first and second mapping tables to construct a snapshot of the SSD.

3. The invention according to claim 2, wherein:

the SSD executes a write in response to a write command received and updates the first and second mapping tables with data in response to executing a write command.

4. The invention according to claim 3, wherein:

the SSD executes a redirect-on-write for the write command received, and updates the second mapping table with data indicating the current view of the SSD.

5. The invention according to claim 4, wherein:

the SSD updates the first mapping table with data indicating a point-in-time copy of the SSD prior to the write command, and,

a plurality of first and second mapping tables to enable the taking of multiple snapshots.

6. The invention according to claim 3, wherein:

the SSD sets data to indicate a snapshot is to be taken; and

,

the SSD executes a redirect-on-write for the write command received.

7. The invention according to claim 6, wherein:

the SSD updates the first and second mapping tables in response to data set by the SSD indicating a snapshot is to be taken.

8. The invention according to claim 7, wherein:

firmware resides in the SSD for updating the first and second mapping table; and

,

a plurality of SSDs for use on a storage system storing data on at least one of the SSDs to enable the taking of a system level data snapshot on data sets stored in the SSDs.

9. The invention according to claim 4, wherein:

means for setting data indicia are present to trigger a snapshot;

the SSD updates the first mapping table with data indicating a point-in-time copy of the SSD prior to the redirect-on-write; and

,

the SSD updates the second mapping table with data indicating the current view of the SSD.

10. The invention according to claim 9, further comprising:

a plurality of first and second mapping tables to enable the taking of multiple snapshots;

means for setting up the first and second mapping tables with pointers to data, and means for terminating a snapshot, including means for discarding a snapshot table; and

,

a plurality of SSDs for use on a storage system storing data on at least one of the SSDs to enable the taking of a system level data snapshot on data sets stored in the SSDs.

11. The invention according to claim 3, further comprising:

a plurality of SSDs for use on a storage system storing data on at least one of the SSDs to enable the taking of a system level data snapshot on data sets stored in the SSDs.

12. A method for a Solid State Disk snapshot comprising the steps of:

storing data on a solid date disk (SSD);

providing a first mapping table for address translation for the SSD; and

,

providing a second mapping table for address translation for the SSD;

wherein said SSD is capable of a point in time copy of the SSD through the data held in the first and second mapping tables.

13. The method according to claim 12, comprising the steps of:

storing in the first mapping table data relating to the snapshot of the SSD;

storing in the second mapping table data relating to the current view of the SSD;

constructing the snapshot of the SSD using the data in the first and second mapping tables.

14. The method according to claim 13, comprising the steps of:

executing a write command;

checking for a snapshot command, and upon receipt of a snapshot command performing the construction of the snapshot.

15. The method according to claim 14, comprising the steps of:

executing a redirect-on-write for the write command;

updating the first mapping table with data indicating a point-in-time copy of the SSD prior to the redirect-on-write;

providing the taking of multiple snapshots for use on a storage system storing data on at least one of the SSDs; and

,

enabling on at least one of the plurality of SSDs the taking of a system level data snapshot on data sets stored in the SSDs.

16. The method according to claim 15, comprising the steps of:

checking for the snapshot command prior to the write command;

terminating the snapshot command; and

,

providing a plurality of first and second mapping tables to enable the taking of multiple snapshots at the same time.

17. The method according to claim 13, comprising the steps of:

checking for a snapshot command;

checking for a write command, and executing a redirect-on-write for the write command;

checking for whether to start a point-in-time copy in response to the snapshot command, and performing the start in time copy if the snapshot command is received, and, terminating the snapshot command if the snapshot command is not received.

18. The method according to claim 17, comprising the steps of:

clearing data from the first mapping table in the event the snapshot command is terminated;

providing a plurality of first and second mapping tables to enable the taking of multiple snapshots at the same time; and

,

updating the second mapping table with data relating to the current view.

19. The method according to claim 13, comprising the steps of:

checking for a snapshot command;

checking for a write command, and executing a redirect-on-write for the write command;

checking for whether to start a point-in-time copy in response to the snapshot command, and performing the start in time copy if the snapshot command is received;

updating the first mapping table with data indicating a point-in-time copy of the SSD prior to the redirect-on-write;

updating the second mapping table with data relating to the current view in the event a snapshot copy is received; and

,

providing a plurality of first and second mapping tables to enable the taking of multiple snapshots at the same time.

20. A system for taking a point-in-time copy of a SSD storage system comprising:

means for storing data comprising a SSD;

said SSD storage means having means for address translation comprising a first lookup tale, said first lookup table holding data relating to a point-in-time copy of the SSD;

said SSD storage means having means for address translation comprising a second lookup table, said second lookup table holding data relating to the current view of the SSD;

means for writing data, said data writing means comprising means for executing a redirect-on-write;

wherein, said SSD uses the first and second lookup tables to construct a snapshot of the SSD;

means for setting data indicia to indicate whether to take a snapshot;

means for updating said first and second lookup tables, with data pointers, in response to said data indicia setting means indicating to take a snapshot;

a plurality of first and second lookup tables on a plurality of SSDs to enable the taking of multiple snapshots;

means for enabling on at least one of said plurality of SSDs the taking of a system level data snapshot on data sets stored in said SSDs; and

,

means for terminating snapshot data in response to a command to terminate a snapshot.