HP StorageWorks 8000 NAS - Manual (Page 102)

100 Managing Your Storage
Replicating Data with Snapshots
Using Snapshots
A snapshot is a read-only picture of a file volume at a specific point in time.
When you create a file volume, the snapshot of that file volume is of zero
length. However, as you modify the file volume, the snapshot tracks changes
between the original file volume and the modified file volume. If an error
occurs and you want to revert to the previous version, you can use the
snapshot data and the unmodified parts of the original file volume to quickly
and easily construct the file volume.
When you set up a snapshot, consider how quickly the file's data will change,
and how often you will delete snapshots and start over. You have the option
to size snapshots relatively small and let them autogrow. As they reach the
limit that you establish, their size can increase by approximately 10 percent
to accommodate the changes. This flexibility lets you set the snapshot and not
worry about a specific size.
After you specify a size, you must define an expiration date. When the
snapshot expires, the system automatically deletes it. Consider your overall
backup strategy in light of the snapshot expiration date. For example, you
may want to take a snapshot of your data for a specified amount of time, then
when you are certain that you have a backup of your system, delete the
snapshot and begin the snapshot process again.
The system treats snapshots as part of a regular file volume. Snapshots
appear in the Snapshot Summary. The Snapshot Summary screen displays:
■ Snapshot name
■ File volume the snapshot is a copy of
■ Volume group the snapshot is a part of
■ Space allocated to the snapshot
■ Space used by the snapshot
■ Space available for the snapshot
■ Whether autogrow or notification is enabled and what the notification
percentage is
■ Expiration date of the snapshot
■ Share count
You can identify a snapshot by the camera icon in the tree. You can create,
edit, delete, and schedule snapshots.