9.5 HP P4000 Remote Copy User Guide (AX696-96089, September 2011)

Best practices
Remote snapshots with volume replication
Use remote snapshots in conjunction with local, synchronous volume replication, known as Network
RAID. Using remote snapshots alone, any data written to the primary volume since the most recent
remote snapshot was created will be unavailable if the primary volume is unavailable.
However, you can lessen the impact of primary volume failure by using Network RAID. Network
RAID allows you to create up to four copies of a volume on the same cluster of storage systems as
the primary volume. The only limitation is that the cluster must contain at least as many storage
systems as replicas of the volume. Replicating the volume within the cluster ensures that if a storage
system in the cluster goes down, replicas of the volume elsewhere in the cluster will still be available.
For more information about Network RAID and data protection levels, see the chapter “Provisioning
Storage” in the HP P4000 SAN Solution User Guide.
Example configuration
“High availability example configuration” (page 33) uses three storage systems per cluster. However,
this scenario can use any number of storage systems. For information about creating clusters and
volumes, see the HP P4000 SAN Solution User Guide.
• In the production location, create a management group and a cluster of three storage systems.
• Create volumes on the cluster and set the data protection level to Network RAID-10.
• Configure the production application server to access the primary volume via iSCSI.
• In the backup location, create a second management group and a cluster of three storage
systems.
• Create a schedule for making remote snapshots of the primary volume. See “Scheduling remote
snapshots” (page 21).
NOTE: Data protection levels are set independently for primary and remote volumes.
How it works
If one of the storage systems in the primary location fails, the primary volume will still be available.
If all of the storage systems fail, or if the application server fails, then failover to the backup
application server occurs, and the remote snapshot(s) becomes available.
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