Administrator Guide

must be greater than the number of existing snapshots in the replication set, regardless of whether snapshot history is
enabled. If you select a snapshot retention count value that is less than the current number of snapshots, an error message
is displayed. Thus, you must manually delete the excess snapshots before reducing the snapshot count setting. When the
snapshot count is exceeded, the oldest unmapped snapshot will be discarded automatically.
● The snapshots are named basename_nnnn where _nnnn starts at 0000 and increments for each subsequent snapshot.
If primary volume snapshots are enabled, snapshots with the same name will exist on the primary and secondary systems.
The snapshot number is incremented each time a replication is requested, whether or not the replication completes — for
example, if the replication was queued and subsequently removed from the queue.
● If the replication set is deleted, any existing snapshots automatically created by snapshot history rules will not be deleted.
You will be able to manage those snapshots like any other snapshots.
● Manually creating a snapshot will not increase the snapshot count associated with the snapshot history. Manually created
snapshots are not managed by the snapshot history feature. The snapshot history feature generates a new name for the
snapshot that it intends to create. If a volume of that name already exists, the snapshot history feature will not overwrite
that existing volume. Snapshot numbering will continue to increment, so the next time the snapshot history feature runs, the
new snapshot name will not conflict with that existing volume name.
● A snapshot created by this feature is counted against the system-wide maximum snapshots limit, with the following result:
○ If the snapshot count is reached before the system limit then the snapshot history is unchanged.
○ If the system limit is reached before the snapshot count then the snapshot history stops adding or updating snapshots.
● A mapped snapshot history snapshot will not be deleted until after it is unmapped.
● The snapshot basename and snapshot retention count settings only take effect when snapshot history is set to secondary or
both, although these settings can be changed at any time.
● You can set the retention priority for snapshots to the following. In a snapshot tree, only leaf snapshots can be deleted
automatically.
Table 22. Snapshot retention priority
Retention
priority
Description
never-delete Snapshots will never be deleted automatically to make space. The oldest snapshot in the snapshot history
will be deleted once the snapshot count has been exceeded. This is the default.
high Snapshots can be deleted after all eligible medium-priority snapshots have been deleted.
medium Snapshots can be deleted after all eligible low-priority snapshots have been deleted.
low Snapshots can be deleted. This parameter is unrelated to snapshot history, and because the default is
never delete, snapshot history snapshots will normally not be affected in a low virtual memory situation.
When this option is disabled, snapshot history will not be kept. If this option is disabled after a replication set has been
established, any existing snapshots will be kept, but not updated.
Create a replication set from the Volumes topic
1. In the volumes table, select a volume or snapshot to use as the primary volume.
2. Select Action > Create Replication Set. The Create Replication Set panel appears.
3. If the selected volume is in a volume group, source options appear.
● To replicate the selected volume only, select Single Volume. This option is the default.
● To replicate all volumes in the volume group, select Volume Group.
4. Enter a name for the replication set. The name is case sensitive and can have a maximum of 32 bytes. It cannot already exist
in the system, include leading or trailing spaces, or include the following characters: " , < \
5. Optional: Select a peer system to use as the secondary system for the replication set.
6. Optional: Select a pool on the secondary system. By default, the pool that corresponds with the pool in which the primary
volume resides is selected. The selected pool must exist on the remote system.
7. Optional: If Single Volume is selected, enter a name for the secondary volume. The default name is the name of the primary
volume. The name is case sensitive and can have a maximum of 32 bytes. It cannot already exist on the secondary system or
include the following: " , < \
8. Optional: Specify the Queue Policy action to take when a replication is running and a new replication is requested.
9. Optional: Select the Secondary Volume Snapshot History check box to keep a snapshot history on the secondary system
for the secondary volume.
● Set the Retention Count to specify the number of snapshots to retain.
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Working in the Volumes topic