Method and Apparatus for Data Recovery System Using Storage Based Journaling

• US 20090019308A1
• Filed: 06/20/2008
• Published: 01/15/2009
• Est. Priority Date: 06/26/2003
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Amano, Takashi
• Granted Patent: US 7,761,741 B2
• Time in Patent Office: Days
• US Class Current: 714/19
• CPC Class Codes: G06F 11/1469 Backup restoration techniques
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: G06F 2201/84 Using snapshots, i.e. a logical point-in-time copy of the data
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

A storage system maintains a journal and a snapshot of one or more data volumes. Two journal entry types are maintained, an AFTER journal entry and a BEFORE journal entry. Two modes of data recovery are provided: “fast” recovery and “undo-able” recovery. A combination of both recovery modes allows the user to quickly recover a targeted data state.

Claims

1. A method for data recovery in a data storage system comprising:

receiving I/O requests from a host machine, the I/O requests being directed to a production volume, the I/O requests including write requests;

producing an original snapshot of the production volume, the original snapshot representative of a first data state of the production volume;

servicing the write requests, including performing write operations on the production volume to produce an updated production volume, the updated production volume having a second data state;

storing a plurality of first journal entries, each first journal entry corresponding to one of the write requests and containing data in the production volume that is to be overwritten by the write request;

performing a recovery operation comprising steps of;

applying one or more first journal entries to the original snapshot to produce an updated snapshot, the updated snapshot having a third data state that is a data state of the production volume at a point in time between the first data state and the second data state; and

restoring the third data state on the production volume based on the updated snapshot by copying the updated snapshot to the production volume to the third data state so that the data recovery can be performed on the production volume in the third data state; and

performing a re-recovery operation comprising steps of;

making a copy of the copy of the original snapshot to produce a second copy of the original snapshot;

applying the one or more first journal entries to the second copy of the original snapshot to produce a second updated snapshot; and

copying the second updated snapshot to the production volume to restore the production volume to the third data state.

2. The method of claim 1,

wherein the re-recovery operation can be performed if an error occurred during the step of applying the one or more first journal entries to the original snapshot.

5. The method of claim 1, further comprising performing a re-recovery operation comprising steps of:

making a copy of the copy of the original snapshot to produce a second copy of the original snapshot;

applying the one or more first journal entries to the second copy of the original snapshot to produce a second updated snapshot; and

copying the second updated snapshot to the production volume to restore the production volume to the third data state,

wherein the re-recovery operation can be performed if an error occurred during the step of applying the one or more first journal entries to the original snapshot.

6. The method of claim 1 further comprising:

producing a copy of the original snapshot;

applying the one or more first journal entries to the copy of the original snapshot to produce the updated snapshot; and

copying the updated snapshot to the production volume to restore the production volume to the third data state.

7. The method of claim 1 further comprising:

copying the original snapshot to the production volume thereby restoring the production volume to the first data state; and

applying the one or more first journal entries to the production volume thereby restoring the production volume to the third data state.

8. The method of claim 1 further comprising:

applying the one or more first journal entries to the copy of the original snapshot to produce the updated snapshot; and

copying the updated snapshot to the production volume to restore the production volume to the third data state.

9. The method of claim 1 further comprising:

producing a current snapshot of the updated production volume, the current snapshot representative of the second data state;

producing a copy of the original snapshot;

applying the one or more first journal entries to the copy of the original snapshot to produce the updated snapshot; and

copying the updated snapshot to the production volume to restore the production volume to the third data state.

3. The method of claim, further comprising:

producing a current snapshot of the updated production volume, the current snapshot representative of the second data state; and

restoring the first data state on the production volume from the original snapshot, wherein the step of applying includes applying the one or more first journal entries to the production volume to restore the production volume to the third data state.

4. The method of claim 3, further comprising at a time subsequent to the data recovery, restoring the second data state of the production volume by copying the current snapshot to the production volume.