HP StorageWorks 2300 Modular Smart Array reference guide (500911-001, January 2009)

24 Using Storage Management Utility (SMU)
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.
Figure 2 Rolling back a master volume
About the Volume Copy feature
Volume Copy is a licensed feature that enables you to copy a volume or a snapshot to a new standard
volume.
While a snapshot is a point-in-time logical copy of a volume, the volume copy service creates a complete
"physical" copy of a volume within a storage system. It is an exact copy of a source volume as it existed at
the time the volume copy operation was initiated, consumes the same amount of space as the source
volume, and is independent from an I/O perspective. Volume independence is a key distinction of a
volume copy (versus a snapshot, which is a "virtual" copy and dependent on the source volume).
Benefits include:
• Additional data protection. An independent copy of a volume (versus logical copy through snapshot)
provides additional data protection against a complete master volume failure. If the source master
volume fails, the volume copy can be used to restore the volume to the point in time the volume copy
was taken.
• Non-disruptive use of production data. With an independent copy of the volume, resource contention
and the potential performance impact on production volumes is mitigated. Data blocks between the
source and the copied volumes are independent (versus shared with snapshot) so that I/O is to each
set of blocks respectively; application I/O transactions are not competing with each other when
accessing the same data blocks.
MasterVolume-1
Snap Pool-1
Snapshot-1
(Wed Jan 18 22:37:17 2008)
Preserved Data
Modified Data
(Thur Jan 22 21:20:30 2008)
MasterVolume-1
Snap Pool-1
Snapshot-1
Modified Data
(Thur Jan 22 21:20:30 2008)
When you use the rollback feature, you
can choose to exclude the modified data,
which will revert the data on the master
volume to the preserved data when
the snapshot was taken.
(Wed Jan 18 22:37:17 2008)
Preserved Data
Or you can choose to include the modified
data since the snapshot was taken, which
will revert the data on the master volume
to the current snapshot.