HP 3PAR InForm OS 3.1.1 Concepts Guide

causes them to lose synchronization with each other, which is corrected by resynchronizing the
two volumes as described in the InForm OS CLI Administrator’s Manual and the InForm OS
Management Console Online Help. No special license is required to create a physical copy of a
volume.
Physical copies can be created and managed in groups to reduce the number of management
tasks. You can create a consistent group physical copies form a list of virtual volumes, and group
physical copies into autonomic groups that are managed as one physical copy.
A physical copy can only be made from a volume with enough free space to accommodate writes
to that volume during the physical copy operation. In addition, the destination volume must meet
the following conditions:
• It must have snapshot space associated with.
• It must have at least as much user space as the volume being copied.
• It must not be exported to a host.
For the maximum number of physical copies that can be created with your specific system
configuration, go to the Single Point of Connectivity Knowledge (SPOCK) website
http://spock.corp.hp.com/index.aspx.
NOTE: If you create a TPVV copy of a fully-provisioned virtual volume, you cannot create a
fully-provisioned copy of that TPVV at a later time. A fully-provisioned virtual volume cannot be
converted to a TPVV, then converted back to a CPVV
Virtual Copy Snapshots
A virtual copy is a snapshot of another virtual volume. You can make virtual copies of base volumes,
physical copies, or other virtual copies. Virtual copies are created using copy-on-write techniques
available only with the HP 3PAR Virtual Copy Software license. Unlike a physical copy which
duplicates the entire base volume, a virtual copy only records the changes to the original volume.
This allows an earlier state of the original volume to be recreated by starting with the current state
and rolling back all of the changes that have been made since the virtual copy was created.
The system allows you to make a maximum of 500 virtual copies of a base volume. Up to 256
virtual copies can be read/write copies. The maximum number of virtual copies that can be created
on a system is determined by the system configuration. For the maximum number of virtual copies
that can be created with your specific system configuration, go to the Single Point of Connectivity
Knowledge (SPOCK) website http://spock.corp.hp.com/index.aspx.
Virtual copies can be created and managed in groups to reduce the number of management tasks.
You can create a consistent group virtual copies form a list of virtual volumes, and group virtual
copies into autonomic groups that are managed as one virtual copy.
NOTE: Virtual copies are consistent at the virtual volume level, but not at the host filesystem or
application level. In other words, virtual copies only preserve the data that was written on the
source virtual volume before the virtual copy is created. Virtual copies do not preserve the data
that is resident within the application or filesystem buffers and is not flushed to disk before the
virtual copy is created.
HP offers optional HP 3PAR Recovery Manager DBA software to enable application-level consistent
snapshots. Contact HP Customer Support for more information.
Virtual Copy Snapshot Relationships
Base volumes are always read/write, but virtual copies can be read/write or read-only. The rules
that govern the relationships between a base volume and its virtual copies are based upon the
difference between read/write and read-only volumes. Read-only and read/write copies must
alternate. You can only make a read-only copy of a read/write volume, and you can only make
a read/write copy of a read-only volume. Since base volumes are always read/write, you can
46 Virtual Volumes