METHOD AND APPARATUS FOR BACKUP AND RECOVERY USING STORAGE BASED JOURNALING

• US 20100274985A1
• Filed: 07/12/2010
• Published: 10/28/2010
• Est. Priority Date: 06/26/2003
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Yamagami, Kenji
• Granted Patent: US 8,234,473 B2
• Time in Patent Office: Days
• US Class Current: 711/162
• CPC Class Codes: G06F 11/1448 Management of the data involved in backup or backup restore
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: G06F 11/3485 for I/O devices
• CPC Class Codes: G06F 2201/81 Threshold
• CPC Class Codes: G06F 2201/84 Using snapshots, i.e. a logical point-in-time copy of the data
• CPC Class Codes: Y10S 707/99952 Coherency, e.g. same view to multiple users
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99955 Archiving or backup

Abstract

A storage system maintains a journal of journal entries and at lease one snapshot of one or more data volumes. By assigning a unique sequence number to journal and snapshot, it is easy to find a journal which can be applied to the snapshot. A technique is described for detecting an overflow condition of running out of journal space and recovering the journal space.

Claims

1. A storage system coupled to a host computer via a network comprising:

a data volume storing write data from the host computer;

a snapshot storing area storing a plurality of snapshots;

a journal storing area storing journal entries including a journal entry between the first point in time and the second point in time; and

a storage controller to conduct write operations according to write requests received from the host computer, to manage snapshot operations to store a plurality of snapshots including the first snapshot and the second snapshot, and to perform data recovery with a target time using said journal entries and a selected snapshot among said plurality of snapshots,

wherein the storage system manages journal operations to record the journal entries, and to apply at least one of the journal entries to one of said plurality of snapshots.

2. The storage system according to claim 1,

wherein said plurality of snapshots includes a first snapshot of at least a portion of the data volume at a first point in time and a second snapshot of said at least a portion of the data volume at a second point subsequent to the first point in time,

wherein in response to a data recovery request with a target time between the first point in time and the second point in time, the storage controller selects the first snapshot based on the target time, selects at least one of the journal entries corresponding to a write operation conducted between the first point in time and the target time, and recovers data of the portion of the data volume at the target time by using the first snapshot and a portion of at least one of the journal entries selected.

3. The storage system according to claim 2,

wherein said storage controller monitors the journal storing area and determines whether to apply the journal entries to said one of said plurality of snapshots based on the monitored results.

4. The storage system according to claim 3,

wherein said storage controller determines to apply the journal entries so that a predetermined amount of free space is maintained for said journal storing area.

5. The storage system according to claim 2,

wherein said journal entry is made for each write operation issued from the host computer.

6. A storage system for processing data comprising:

a production data store receiving write operations from a host device;

a snap shot data store storing one or more snapshots of at least a portion of the production data store;

a journal data store storing one or more journal entries; and

a controller,

wherein in response to a data recovery request specifying a target time, said controller selects a snapshot based on a target time, determines a beginning journal entry based on sequence numbers associated with the journal entries and a sequence number of the selected snapshot, updates the selected snapshot by applying the beginning journal entry to it, and performs additional updates to the selected snapshot by applying journal entries that are later in time than the beginning journal entry and earlier in time than the target time.

7. The storage system according to claim 6,

wherein said controller accesses the production data store and the snapshot data store to store one or more snapshots of at least a portion of the production data store on the snapshot data store, and accesses the journal data store to record a journal entry for each write operation from the host device.

8. The storage system according to claim 7,

wherein said controller updates one of the snapshots with a portion of the journal entries so that it releases space in the journal data store.

9. The storage system according to claim 7,

wherein said controller updates one of the snapshots with a portion of the journal entries when an amount of free space in the journal data store falls below a first threshold value.

10. The storage system according to claim 8,

wherein said journal entry is made for each write operation issued from the host computer.