Designing Disaster Recovery Clusters using Metroclusters and Continentalclusters, Reprinted October 2011 (5900-1881)

Remote Copy and Thin Provisioning
A Common Provisioning Group (CPG) is a user-created storage pool available to all volumes
associated with it. There are two types of virtual volumes, which draw spaces from CPGs that can
be used with Remote Copy:
• Thinly Provisioned Virtual Volumes (TPVVs)
• Fully provisioned Virtual Volumes.
For TPVVs, all data and snapshot space is allocated on demand from a CPG, and for fully
provisioned virtual volumes, only the snapshot space is allocated on demand from the CPG. All
volumes used with Remote Copy must be TPVVs or fully provisioned virtual volumes.
Remote Copy Volume Group Modes
There are two modes used by Remote Copy volume groups: synchronous and asynchronous
periodic.
In synchronous mode, a host-initiated write is performed on both the primary and the backup
storage systems before host writes are acknowledged. In the case of a disaster that affects the
primary storage system, the copy stored on the backup storage server at the remote site, can be
immediately used to continue the application. This copy is an exact replica of the primary storage
system.
In the asynchronous periodic mode, host writes are performed only on the primary storage system
and the host write is acknowledged when the data is written into cache on the primary storage
system. The primary and backup volumes are resynchronized periodically at scheduled time or
synchronization is manually initiated. If between two synchronizations, an area of the volume is
written to multiple times, only the last write needs to be synchronized with the other storage system.
NOTE: In Metrocluster with 3PAR Remote Copy environment, only synchronous mode is supported.
Remote Copy Target Definitions
As part of the Remote Copy setup process, you must create target definitions on each Remote Copy
system. The target definitions are descriptions that exist on one system in order to identify a Remote
Copy system. For example, the 3PAR storage systems in the Remote Copy pair are each defined
as targets, relative to each other, for Remote Copy operations.
Virtual Domains
The HP 3PAR Virtual Domains facility enables finer grain privileges over system objects such as
volumes and hosts. Domains allow an administrator to create up to 1024 domains, or spaces,
within a 3PAR storage system, where each domain is dedicated to a specific application. A subset
of the 3PAR storage system users has varying privileges over the domains. Domains can be useful
where a single storage system is used to manage data from several different independent
applications Figure 55.
Overview of HP 3PAR Remote Copy Concepts 313