Browse Prior Art Database

A Method and System for facilitating an Undo Operation using an Undo Buffer with an Optional Tape Offload

IP.com Disclosure Number: IPCOM000239350D
Publication Date: 2014-Nov-01
Document File: 4 page(s) / 58K

Publishing Venue

The IP.com Prior Art Database

Abstract

A method and system is disclosed for facilitating an undo operation using an undo buffer with an optional tape offload.

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This is the abbreviated version, containing approximately 51% of the total text.

Page 01 of 4

A Method and System for facilitating an Undo Operation using an Undo Buffer with an Optional Tape Offload

In a FlashCopy pair, a point-in-time snapshot of a volume A is created in a volume B. A reverse-restore feature allows a user to copy contents of the volume B back to the volume A in order to restore the point-in-time snapshot being maintained by the volume B. During the reverse-restore, any modification to data on the volume A, since the FlashCopy

was established, gets overwritten and may no longer be available. However, there may be cases, when a user may want

to later access such modified data of the volume A. For example, in a case where the reverse-restore command was mistakenly issued on the FlashCopy pair. Similarly, such scenario may arise during Peer to Peer Remote Copy (PPRC) failover/failback process as well.

Disclosed is a method and system for facilitating an undo operation using an undo buffer with an optional tape offload. The method and system maintains data in a source volume at a current point-in-time, when a reverse-restore is issued mistakenly or intentionally.

In an embodiment, a temporary volume can be utilized as a target in a FlashCopy relationship with the source volume for executing a reverse-restore command. In accordance with the method and system, to ensure excessive capacity is not depleted on the temporary volume, an optional tape library can be utilized. An undo recovery data can be offloaded

asynchronously to the optional tape library followed by a deletion of the temporary volume.

In accordance with the method and system disclosed herein, an optional flag is set for a command or as an attribute of the source volume itself. The optional flag indicates that the command when executed against the source volume is made undo capable. Accordingly, when the flag is set then the data within the source volume at the current point-in-time is maintained using the algorithm as illustrated in Fig. 1.

1


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Figure 1

In accordance with the embodiment, a temporary volume is created and the source volume that is about to be overwritten is flashed to the temporary volume. The command is thereafter exectuted on the source volume. Subsequently, a metadata in the source volume is set identifying the temporary volume being used to maintain the data. Then, the temporary volume is optionally offloaded to the tape if specified by a user either via a command parameter, an volume attribute, or a storage system attribute. The metadata of the temporary volume is then updated with the location on tape prior to the start of the offload. If the user has not chosen to offload the volume to tape then a timeout needs to be set by the user indicating how long the temporary volume needs to be maintained. The process ultimately establishes a time limit on how long the user has to lat...