Hardware manual

Group Administration Advanced volume operations
10–7
The group always maintains and shows the dependency of a thin clone on a template volume. If you expand
Volumes in the far-left panel, you can choose to display all volumes in alphabetical order or display thin clones
under the template volume on which they depend.
If you replicate a template volume and its attached thin c
lones, the primary and secondary groups maintain the
dependency. For example, you must replicate a template volume before replicating any of its thin clones. On the
secondary group, if you expand
Inbound Replicas in the far-left panel, you can choose to display thin clone
replica sets under the template replica set on which they depend.
In addition, the group maintains and shows the dependency of
a thin clone on a template volume (or a thin clone
replica set on a template replica set), even if a volume (or replica set) changes state, as occurs during failover and
failback operations. For example, if you promote a thin clone replica set to a recovery thin clone, you can still see
the dependency of the recovery thin clone on the template replica set.
Because of this dependency, the group does not allow you to del
e
te a template volume, a template replica set, or a
recovery template if a thin clone, thin clone replica set, or recovery thin clone depends on it. Also, you cannot
disable replication on a template volume until you disable replication on all its thin clones.
Space considerations for template volumes and thin clones
When you convert a standard volume to a template volume:
• Thin provisioning is enabled on the volume, the volume is set
offline, and the volume permission is set to read-
only.
Note: If you are using the Group Manager CLI, you must perform the
se tasks manually before you can
convert to a template volume.
• Volume reserve decreases to the amount of in-use space
(or the minimum volume reserve, whichever is
greater), and free volume reserve becomes unreserved space.
• Snapshot reserve is adjusted, based on the new volume reserve
. If necessary to preserve existing snapshots, the
snapshot reserve percentage is increased.
When you create a thin clone volume, it has the same reported size
and contents as the template volume. If you
mount the thin clone, you can see the data that the thin clone shares with the template volume.
The group allocates only the minimum volume reserve when you first create a thin clone. The group al
locates
additional space if you specify snapshot reserve for the thin clone. Just as with a standard, thin provisioned volume,
as you write to a thin clone, the group allocates more space and increases the volume reserve.
In the Volume Status window for a thin clone volume, the Vo
lume Space table shows the space utilization for the
thin clone, including the in-use space, which is the portion of volume reserve that is storing data unique to the thin
clone. When you first create a thin clone, it has zero in-use space.
In the Volume Status window for a thin clone volume, the Shared
Space table (only appears for thin clones) shows
the amount of space that is shared with the template volume and the unshared (in-use) space. As you write to the
thin clone, unshared (in-use) space increases. In some cases, when you write to a thin clone, shared space can
decrease (for example, if you are overwriting shared data).
Free space in the Shared Space table shows the amount of unwritten
thin clone space (tha
t is, the reported volume
size minus the combined shared space and unshared space). This represents the amount of data you can write to the