HP 3PAR Operating System Software - Manual (Page 191)

How Volume Groups Work
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, 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, 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 a snapshot is
lengthened.
If the snapshot process takes too long, and therefore Remote Copy blocks writes for too long, some
host writes might time out.
Rules for Forming Volume Groups
The group of virtual volumes in a Remote Copy volume group:
•
must be located on the same storage system
•
can be logically related
•
can be volumes for which there is a cross-volume ordering of writes
•
must not exceed the maximum of 100
•
must be one of these types:
Thinly Provisioned Virtual Volumes (TPVVs) with snapshot space ◦
◦ Fully provisioned virtual volumes
◦ Read/write (RW) snapshots (see “Rules for Adding Snapshots to Volume Groups”
(page 191) )
Additional Information: “Limits on Volumes that Concurrently Synchronize” (page 197)
How Volume Groups Are Named
When you create and name a volume group on the primary system (using the creatercopygroup
command), Remote Copy automatically creates and names the associated secondary volume group
on the backup system. The secondary volume group is named:
<primary_group_name>.r<primary_system_system_ID>
For example, if the primary volume group is Group1 and the primary system ID is 96, Remote
Copy names the secondary volume group Group1.r96.
Additional Information:
•
“Creating Remote Copy Volume Groups” (page 71)
•
“About the Remote Copy Commands” (page 222)
Rules for Adding Snapshots to Volume Groups
You can add read/write (RW) snapshots to volume groups:
•
You can add one RW snapshot per virtual volume to a volume group.
•
You cannot add both a snapshot and the base volume for that snapshot to the same volume
group.
•
You cannot add a snapshot to more than one volume group.
How Volume Groups Work 191