Method and apparatus for data recovery using storage based journaling

• US 20060149798A1
• Filed: 02/28/2006
• Published: 07/06/2006
• Est. Priority Date: 07/16/2003
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Yamagami, Kenji
• Granted Patent: US 8,145,603 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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

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. (canceled)

2. 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 first snapshot of at least a portion of the data volume for a first point i time, the first point in time represented by first information that specifies a time when the first snapshot is taken, the snapshot storing area further storing a second snapshot of the portion of the data volume for a second point in time, the second point in time represented by second information that specifies a time when the second snapshot is taken;

a journal storing area storing journal entries, wherein the journal entries comprise the write data and time ordering information specifying write ordering of write operations to the data volume; 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 manage journal operations to record the journal entries,

wherein the first and second information are associated with the time ordering information to specify time ordering among a time when one of the write operations is conducted, the first point in time, and the second point in time,

wherein the storage controller releases at least one of the stored journal entries,

wherein when receiving a data recovery request with a first target time between the first point in time and the second point in time, the storage controller determines if at least one of the journal entries is stored in the journal storing area to perform the data recovery request, selects one of the first or second snapshot based on the first information, the second information and the first target time to copy the selected snapshot to a recovery volume, and selects at least one of the journal entries corresponding to the write operations conducted between one of the first or second point in time associated with the selected snapshot and the first target time based on one of the first or second information associated with the selected snapshot, the time ordering information, and the fist target time to recover data of the portion of the data volume at the first target time by applying the selected journal entries to the copied snapshot in the recovery volume.

3. The storage system of claim 2, wherein when receiving a data recovery request with a second target time between the first point in time and the second point in time, the storage controller selects one of the first or second snapshot based on the first information, the second information, and the second target time to copy the selected snapshot to the recovery volume, and selects at least one of the journal entries corresponding to the write operations conducted between the second target time and one of the first or second point in time associated with the selected snapshot based on one of the fist, or second information associated with the selected snapshot, the time ordering information and the second target time to recover data of the portion of the data volume at the second target time by applying the selected journal entries to the selected snapshot in the recovery volume.

4. The storage system of claim 2, wherein the time ordering information includes time information and/or sequence number.

5. The storage system of claim 4, wherein the first and second information include time information and/or sequence number.

6. The storage system of claim 2, wherein the write data stored in the journal storing area are stored in chronological order.

7. The storage system of claim 2, wherein the snapshot storing area and/or the journal storing area are configured with storage volumes.

8. The storage system of claim 2, wherein at least one of the journal entries are stored in the journal storing area before storing one of the plurality of snapshots in the snapshot storing area.

9. The storage system of claim 2, wherein the journal operations are started prior to starting the snapshot operations.

10. The storage system of claim 2, wherein the selected snapshot is closest in time to the first target time.

11. The storage system of claim 2, wherein the selected snapshot is prior in time to the first target time.