HP StorageWorks 2000 Modular Smart Array Reference Guide (481599-003, August 2008)

Chapter 3 Managing Storage 107
Reverting to Original Data
The snapshot service has two features for reverting data back to original data:
■ Deleting only modified data on a snapshot
■ Rolling back the data in a master volume
For snapshots that have been made accessible as read-write, you can delete just the
modified (write) data that was written directly to a snapshot. When the modified
data is deleted, the snapshot data reverts to the original data that was snapped. This
feature is useful for application test, for example. You might want to test some code,
which writes data to the snapshot. Rather than having to take another snapshot, you
can just delete any write data and start again.
The roll back feature enables you to revert the data in a master volume to the data
that existed when a specified snapshot was created (preserved data). You also have
the option of rolling back to include the modified (write) data on the snapshot since
the snapshot was taken. For example, you might want to take a snapshot, mount that
snapshot for read/write, and then install new software on that snapshot for test
purposes. If the software installation is successful, you can roll back the master
volume to the contents of the modified snapshot (preserved data plus the write data).
The following figure shows the difference between rolling back the master volume
to the data that existed when a specified snapshot was created (preserved), and
rolling back preserved and modified data.