Rolling Back A Master Volume - HP P2000 Reference Manual

The storage system allows a maximum number of snapshots to be retained, as determined by an installed
license. For example, if your license allows four snapshots, when the fifth snapshot is taken an error
message informs you that you have reached the maximum number of snapshots allowed on your system.
Before you can create a new snapshot you must either delete an existing snapshot, or purchase and install
a license that increases the maximum number of snapshots.
The snapshot service has two features for reverting data back to original data:
Deleting only modified data on a snapshot. 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 testing an application, 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.
• Rolling back the data in a source volume. The rollback feature enables you to revert the data in a
source volume to the data that existed when a specified snapshot was created (preserved data).
Alternatively, the rollback can include data that has been modified (write data) on the snapshot since
the snapshot was taken. For example, you might want to take a snapshot, mount/present/map that
snapshot for read/write, and then install new software on that snapshot for test purposes. If the
software installation is successful, you can rollback 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.
MasterVolume-1
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.
MasterVolume-1
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.
Figure 2

Rolling back a master volume

Snapshot-1
Preserved Data
(Monday)
Modified Data
(Tuesday)
Snap Pool-1
Snapshot-1
Preserved Data
(Monday)
Modified Data
(Tuesday)
Snap Pool-1
HP P2000 G3 MSA System SMU Reference Guide 27