Hardware manual

Group Administration Basic volume operations
9–2
You can replicate any volume type, resulting in a replica set for the volume. In addition, you can fail over any
volume type, resulting in a recovery version of the volume. However, you can only fail back a standard volume or
a thin clone volume.
Displaying the iSCSI target name and alias
To display the iSCSI target name and public alias for a volume, click Volumes in the lower-left panel, then expand
Volumes, then select the volume name, and then click the Connections tab.
See the online help for information about the data fields and options.
About volume space allocation
It is important to understand how the group allocates space to volumes. This helps you to size volumes correctly.
Although you can modify a volume size, some operating systems and initiators do not easily handle size changes.
When you create a volume, you specify the repor
ted size for the volume, which is the maximum amount of space
that the group might be able to allocate to the volume. You can increase or decrease the reported size.
The reported size is seen by iSCSI initiators. If a write to a volume exceeds the reported size, the wri
te fails, and the
group generates event messages.
The actual amount of pool space that the group alloc
ates to a volume is called the volume reserve. The value of the
volume reserve depends on whether you enable thin provisioning on a volume:
• No thin provisioning – The volume reserve is equal to the reported size
.
• Thin provisioning – If you enable thin provisioning on a volume, the group allocates space based on volume
usage. The volume
reserve is equal to or less than the reported size, depending on volume usage and the thin
provisioning settings. See About thin provisioning.
Space allocated for volume operations (for example, snapsh
ot reserve and local replication reserve) is based on the
volume reserve.
You cannot use space that the group allocates to a volume (or for volume ope
rations) for other purposes. Therefore,
make sure you allocate space only when necessary.
You must fully understand application and workload space require
ments to allocate the correct amount of space.
About volume security and access controls
Online volumes and snapshots are seen on the network as iSCSI targets. It is important to understand how to
protect your iSCSI targets from unauthorized and uncoordinated access by iSCSI initiators. See iSCSI target
security.
Access control records prevent unauthorized
computer access to iSCSI targets (volumes or snapshots). A volume
and its snapshots share a list of access control records. An access control record can apply to the volume, its
snapshots, or both. For example, you can authorize computer access to a volume and its snapshots or only to the
volume.
When you create a volume, you can create
an
access control record for the volume. You can later create additional
access control records (up to 16) for a volume. See Configuring access control records on page 9
-10.