HP 3PAR Operating System Software - Manual (Page 111)

How Volume Groups Work
HP 3PAR Remote Copy functions as if the virtual volumes in a volume group are related and
therefore ensures that the data in the virtual volumes within a volume group maintain write
consistency.
When you start or stop remote-copy operations, HP 3PAR Remote Copy starts and stops operations
for the whole volume group.
When you (or an automated process) create a point-in-time snapshot of virtual volumes in a volume
group, HP 3PAR Remote Copy blocks writes to all volumes in the group in order to ensure a
consistent point-in-time virtual copy of the whole volume group.
CAUTION: Take care not to add too many virtual volumes to one volume group. If a volume
group contains a very large number of virtual volumes, the process of creating snapshots is
lengthened.
If the snapshot process takes too long, some host operations might time out.
Creating Automatic Remote-Copy VV Sets
Starting from HP 3PAR OS 3.1.3, when a remote-copy group is created, the system automatically
creates a new VV set that contains the same volumes as those in the remote-copy group. These VV
sets can be exported to a host or host set, and can be used to assign quality of service (QoS) rules.
The QoS rule can be used to limit the maximum amount of bandwidth or I/O per second that the
system grants the VV set at any given time while preserving synchronous data replication.
VV sets are assigned the prefix RCP_x, where x is the name of the remote-copy group. In case of
naming conflicts, the VV set will be named RCP_x.0, then RCP_x.1, and so on. If there is
insufficient space to append the prefix or extension, x is truncated. VV sets can be renamed; a
renamed VV set retains its link to the remote-copy group.
When volumes are added to or removed from the remote-copy group, the VV set is automatically
updated, and the VV set is deleted if the remote-copy group is deleted.
Use of the following CLI commands result in operations on VV sets:
•
admitrcopyvv
•
removercopyvv
•
creatercopygroup
•
removercopygroup
If adding a volume to a remote-copy group would create a LUN conflict in the remote-copy group
VV set, the admitrcopyvv command is rejected. To add another volume to the group, either the
conflicting LUN must be removed, or the export of the VV set must be replaced by a manually
created set that does not contain the new volume.
To maintain consistency between the volume group and the VV set, you cannot directly change
the members of the VV set or remove the VV set; an attempt to do so will fail. Instead, make changes
directly to the members of the remote-copy group.
If a set being manipulated by either of the following commands is an automatic remote-copy VV
set, the operation is rejected:
•
createvvset -add
•
removevvset
How Volume Groups Work 111