HP StorageWorks XP Cluster Extension Software Administrator Guide (T1656-96035, April 2010)

Cluster Extension does not support configurations in which the application service's data disk set is
spread over two or more XP disk arrays.
Figure 2 Consolidated-site configuration
.
Supported XP Continuous Access Software configurations and fence levels
XP Continuous Access Software offers three modes of replication:
• Synchronous replication
• Asynchronous replication
• Journal replication
For the replication modes supported by specific versions of XP Cluster Extension, see the HP SPOCK
website: http://www.hp.com/storage/spock. For information about synchronous and asynchronous
replication modes, see the HP StorageWorks XP Continuous Access Software User Guide. For
information about journal replication, see the HP StorageWorks XP Continuous Access Journal Software
User Guide.
The XP Continuous Access Software fence level is used to configure the remote replication feature of
an XP disk array based on needs for application service availability, data concurrency, and replication
performance. XP Cluster Extension supports all XP Continuous Access Software fence levels: NEVER,
DATA, and ASYNC (includes JOURNAL).
XP Cluster Extension is supported with XP Continuous Access Software in the configurations described
in the HP StorageWorks SAN Design Reference Guide, available at http://www.hp.com/go/
sdgmanuals.
XP Cluster Extension server configurations
The ideal cluster configuration for XP Cluster Extension consists of at least four servers (two at each
site) and separate redundant communications links for cluster heartbeats, client access, and XP
Continuous Access Software. Installing communications interfaces in pairs allows failover and prevents
single points of failure (SPOFs). Using four servers provides faster recovery from a system failure by
allowing local application services to fail over to a local cluster system instead of the remote system.
On the remote site, HP recommends that two systems be available in case one system experiences a
hardware or power failure. In addition to at least four servers, the MNS configuration requires an
additional node per cluster, located at a third site so that whenever a disaster affects either the local
XP Cluster Extension features14