HP StorageWorks P9000 Cluster Extension Software Administrator Guide (TB534-96009, February 2011)

Each cluster host node needs redundant FC or SCSI I/O paths to the disk array. Individual hosts
cannot be connected to both the primary (P-VOL) and the secondary (S-VOL) copy of the application
disk set.
HP recommends a minimum of two cluster host nodes per site. This allows for a preferred local
failover in case of a system failure. Local failover operations are faster than a remote failover
between disk arrays because the mirroring direction of the disks does not need to be changed.
P9000 Cluster Extension can be deployed in environments where several clusters use the same
pair of disk arrays. Although P9000 and XP disk arrays can be mirrored in various configurations,
P9000 Cluster Extension does not support multiple disk arrays as both primary and secondary disk
arrays. P9000 Cluster Extension supports configurations where two or more disk arrays use one
remote disk array in a logical one-to-one configuration.
CAUTION: P9000 Cluster Extension can operate with only one system at each site, with a single
I/O path between the server system and the disk array and a single link in each direction between
disk arrays.
However, those configurations are not considered highly available, nor are they disaster tolerant.
P9000 Cluster Extension configurations with single points of failure are not supported by HP.
Consolidated-site configuration
In consolidated-site configurations, a single disk array in the secondary (remote) data center is
connected to up to four other primary disk arrays. For an example of a consolidated-site
configuration, see “Consolidated-site configuration” (page 10). The restrictions outlined in
“One-to-one configurations” (page 9) also apply to consolidated configurations. P9000 Cluster
Extension does not support configurations in which the application service's data disk set is spread
over two or more disk arrays.
Figure 2 Consolidated-site configuration
Supported Continuous Access configurations and fence levels
The Continuous Access software offers three modes of replication:
• Synchronous replication
• Asynchronous replication
• Journal replication
For the replication modes supported by specific versions of P9000 Cluster Extension, see the HP
SPOCK website: http://www.hp.com/storage/spock. For information about synchronous and
10 P9000 Cluster Extension features