6.3 HP StoreAll Storage File System User Guide (TA768-96093, June 2013)

18 Creating block snapshots
The block snapshot feature allows you to capture a point-in-time copy of a file system for online
backup purposes and to simplify recovery of files from accidental deletion. The snapshot replicates
all file system entities at the time of capture and is managed exactly like any other file system.
NOTE: You can use either the software method or the block method to take snapshots on a file
system. Using both snapshot methods simultaneously on the same file system is not supported.
The block snapshot feature is supported as follows:
• HP 9320 Storage: supported on the HP P2000 G3 MSA Array System or HP 2000 Modular
Smart Array G2 provided with the platform.
• HP 9300 Storage Gateway: supported on the HP P2000 G3 MSA Array System; HP 2000
Modular Smart Array G2; HP P4000 G2 Models; HP 3PAR F200, F400, T400 and T800s
Storage Systems (OS version 2.3.1 (MU3); and Dell EqualLogic storage array (no arrays are
provided with the 9300 system).
• HP X9720/9730 Storage: no support.
The block snapshot feature uses the copy-on-write method to preserve the snapshot regardless of
changes to the origin file system. Initially, the snapshot points to all blocks that the origin file system
is using (B in the following diagram). When a block in the origin file system is overwritten with
additions, edits, or deletions, the original block (prior to changes) is copied to the snapshot store,
and the snapshot points to the copied block (C in the following diagram). The snapshot continues
to point to the origin file system contents from the point in time that the snapshot was executed.
To create a block snapshot, first provision or register the snapshot store. You can then create a
snapshot from type-specific storage resources. The snapshot is active from the moment it is created.
You can take snapshots via the StoreAll software block snapshot scheduler or manually, whenever
necessary. Each snapshot maintains its origin file system contents until deleted from the system.
Snapshots can be made visible to users, allowing them to access and restore files (based on
permissions) from the available snapshots.
NOTE: By default, snapshots are read only. HP recommends that you do not allow writes to any
snapshots.
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