Snapshots for a non-volatile device

• US 10,318,495 B2
• Filed: 07/11/2013
• Issued: 06/11/2019
• Est. Priority Date: 09/24/2012
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Inventors: Talagala, Nisha, Sundararaman, Swaminathan, Subramanian, Sriram
• Primary Examiner(s): Kim, Paul
• Application Number:
  US13/939,992
• Publication Number:
  US 20140089264A1
• Time in Patent Office: 2,161 Days
• CPC Class Codes: G06F 11/1448 Management of the data involved in backup or backup restore
• CPC Class Codes: G06F 11/1466 to make the backup process non-disruptive
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: G06F 16/21 Design, administration or maintenance of databases
• CPC Class Codes: G06F 3/0616 in relation to life time, e.g. increasing Mean Time Between Failures [MTBF]
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]

Abstract

Apparatuses, systems, and methods are disclosed for snapshots of a non-volatile device. A method includes writing data in a sequential log structure for a non-volatile device. A method includes marking a point, in a sequential log structure, for a snapshot of data. A method includes preserving a logical-to-physical mapping for a snapshot based on a marked point and a temporal order for data in a sequential log structure.

Claims

1. A method comprising:

servicing one or more requests from one or more storage clients to write data to a non-volatile memory device, by writing the data in a sequential log on the non-volatile memory device, the data comprising data segments;

storing logical addresses for the data segments with the data segments in the sequential log;

initializing a snapshot of the data by marking a point in the sequential log;

activating the snapshot for access by a client, wherein activating the snapshot comprises populating a snapshot logical-to-physical mapping by mapping logical addresses stored in the sequential log prior to initializing the snapshot to physical locations of data segments stored in the sequential log prior to initializing the snapshot, the snapshot logical-to-physical mapping differing from a current logical-to-physical mapping;

servicing a client request to access the snapshot, by using the snapshot logical-to-physical mapping to access data stored in the sequential log prior to initializing the snapshot, while preserving data stored in the sequential log subsequent to the initializing the snapshot; and

servicing a client request to access data stored in the sequential log subsequent to the initializing the snapshot, by using the current logical-to-physical mapping.

2. The method of claim 1, further comprising maintaining different validity maps for a plurality of different snapshots of the non-volatile memory device.

3. The method of claim 2, wherein maintaining the different validity maps comprises copying at least a portion of a validity map for a first snapshot in response to a write request received for a second snapshot.

4. The method of claim 2, further comprising retaining, during a storage capacity recovery operation, data marked as valid in one or more of the different validity maps.

5. The method of claim 1, wherein activating the snapshot is in response to an activation event for the snapshot, the activation event occurring separate from and later in time than a creation event for the snapshot.

6. The method of claim 5, wherein the activation event comprises one or more of an activation request for the snapshot, a background activation process processing the snapshot, a scheduled activation event for the snapshot, and a failure event.

7. The method of claim 1, wherein the snapshot comprises a block-level snapshot of logical blocks of the non-volatile memory device.

8. The method of claim 1, further comprising preserving a temporal order for the data in response to a storage capacity recovery event, the storage capacity recovery event writing valid data from a recovered storage region of the sequential log to an append point of the sequential log.

9. The method of claim 8, wherein preserving the temporal order for the data comprises retaining one or more epoch identifiers for the valid data written to the append point of the sequential log.

10. The method of claim 1, wherein marking the point in the sequential log comprises writing an epoch identifier associated with the snapshot to the sequential log.

11. The method of claim 1, wherein marking the point in the sequential log comprises:

incrementing an epoch identifier; and

storing the incremented epoch identifier in one or more metadata headers for data written in the sequential log after the point in the sequential log.

12. An apparatus comprising:

a log storage module configured to service one or more requests from one or more storage clients to write data to a non-volatile memory device, by writing the data in a sequential log on the non-volatile memory device, the data comprising data segments;

a temporal order module configured to store logical addresses for the data segments with the data segments in the sequential log;

a creation module configured to initialize a snapshot of the data by marking a point in the sequential log;

an activation module configured to activate the snapshot for access by a client, wherein activating the snapshot comprises populating a snapshot logical-to-physical mapping by mapping logical addresses stored in the sequential log prior to initializing the snapshot to physical locations of data segments stored in the sequential log prior to initializing the snapshot, the snapshot logical-to-physical mapping differing from a current logical-to-physical mapping;

a snapshot interface module configured to service a client request to access the snapshot, by using the snapshot logical-to-physical mapping to access data stored in the sequential log prior to initializing the snapshot, while preserving data stored in the sequential log subsequent to the initializing the snapshot; and

a non-volatile memory controller configured to service a client request to access data stored in the sequential log subsequent to the initializing the snapshot, by using the current logical-to-physical mapping,

wherein the log storage module, the temporal order module, the creation module, the activation module, and the snapshot interface module comprise one or more of logic hardware and a non-transitory computer readable storage medium storing computer usable program code.

13. The apparatus of claim 12, further comprising a validity module configured to maintain different validity maps for a plurality of different snapshots of the non-volatile memory device.

14. The apparatus of claim 12, wherein the activation module activates the snapshot in response to an activation event for the snapshot, the activation event occurring separate from and later in time than a creation event for the snapshot.

15. The apparatus of claim 14, wherein the activation event comprises one or more of an activation request for the snapshot, a background activation process processing the snapshot, a scheduled activation event for the snapshot, and a failure event.

16. An apparatus comprising:

means for servicing one or more requests from one or more storage clients to write data to a non-volatile memory device, by writing the data in a sequential log on the non-volatile memory device, the data comprising data segments;

means for storing logical addresses for the data segments with the data segments in the sequential log;

means for initializing a snapshot of the data by marking a point in the sequential log;

means for activating the snapshot for access by a client, wherein activating the snapshot comprises populating a snapshot logical-to-physical mapping by mapping logical addresses stored in the sequential log prior to initializing the snapshot to physical locations of data segments stored in the sequential log prior to initializing the snapshot, the snapshot logical-to-physical mapping differing from a current logical-to-physical mapping;

means for servicing a client request to access the snapshot, by using the snapshot logical-to-physical mapping to access data stored in the sequential log prior to initializing the snapshot, while preserving data stored in the sequential log subsequent to the initializing the snapshot; and

means for servicing a client request to access data stored in the sequential log subsequent to the initializing the snapshot, by using the current logical-to-physical mapping.

17. The apparatus of claim 16, further comprising means for preserving a temporal order for the data in response to a storage capacity recovery event, the storage capacity recovery event writing valid data from a recovered storage region of the sequential log to an append point of the sequential log.