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Posts Tagged ‘locked snapshot’

Locked / Busy Snapshots

June 7th, 2009

This is one of those annoying situations that can cause things to come crashing down when you least expect it.

Locked snapshots can happen for several reasons, the obvious ones are that they are the basis of a SnapMirror or SnapVault update (despite both relying on the snapshots, they will only actually lock a snapshot during an active transfer, you can happily delete the snapshots otherwise and this will destroy the replication relationship, more or less). They can also be because of a vol copy, or for a very brief period a snap restore.

2 of the less obvious, but more common reasons are that of a LUN Clone and a FlexClone. Both in principle are fairly similar, but in practice act very different.

Simply a clone will base itself on a snapshot and then create a sparse clone based on this snapshot, and as such the original blocks of data, hence using no data. The clone can then be split, but 99/100 it will be used for some sort of verification or reporting and then removed.

A LUN Clone is the one that causes us most problems. As said, it creates a clone based on a snapshot, but the clone is created within the volume, and only of a particular LUN. This is infact a very similar concept to that of the new Single File FlexClone available in 7.3. Based on a given snapshot, you will have a new LUN created within the same volume as the parent LUN. This will use no storage, and is great for running verifications, or possibly testing or even reporting.

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