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Maintaining Consistency Groups With Space Efficient Volumes

IP.com Disclosure Number: IPCOM000211741D
Publication Date: 2011-Oct-14
Document File: 4 page(s) / 43K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method to automatically recover from failed Consistency Groups (CG) in a mirroring environment without user intervention.

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Maintaining Consistency Groups With Space Efficient Volumes

In current art, mirrored consistency groups (CG) are formed at a defined interval in order to maintain a point-in-time recoverable copy of the data on the secondary system in the event of a disaster, for testing purposes, etc. The problem arises when the consistency group is unable to complete the copy (i.e., form) within the allotted time causing a failure of the CG and suspending the mirroring for the volumes within the CG.

The recovery in this situation requires the user to manually intervene by restarting the mirrored CG after receiving an alert that the failure has occurred. This may take some time to recover, resulting in more updates to the primary volume and a potential for more data to be recovered from backups in the event of a disaster (i.e., the delta between the last successful CG and last backup).

This invention describes a method to automatically recover from failed Consistency Groups (CG) in a mirroring environment without user intervention. This requires a new volume that is hidden from host access and is created by the new module when a mirrored CG is defined. This new volume is known as a space efficient consistency group volume (SECGV). An SECGV is created for every CG when the CG is defined, regardless of the number of volumes within the CG (e.g., a CG may consist of 10 volumes, but only one SECGV is created). This is a space efficient volume that temporarily utilizes capacity, freeing up that capacity once the CG has formed and the CG state restored to good status. This volume utilizes as much available capacity as needed during the forming of the CG and releases all the used space once the CG has formed during a specified interval.

When data is being sent from the primary site to the secondary site, a copy of that data is also written to the SECGV (as stated, using as much space as needed). If the consistency group is formed within the allotted time then the data written on the SECGV is removed.

With this method, when a CG fails to form, the CG is marked in a failed state, and mirroring appears to be suspended (a.k.a., pseudo suspension in new art)...