HP XP Cluster Extension Software Administrator Guide

to another or if you want XP Cluster Extension to check disk states to make sure you can automatically
start an application service on the local disk array.
Fast Failback using Continuous Access
XP Cluster Extension supports the RAID Manager Fast Failback feature. This feature allows the
Continuous Access software to automatically redirect the mirroring direction of a disk pair even if
the remote RAID Manager instance is not available. This ensures the fastest possible recovery to
the original site in case of an application service failover at the alternate site.
XP Cluster Extension configurations
XP Cluster Extension is an array-based solution. It requires at least two XP disk arrays with the
Continuous Access software providing remote mirroring. XP Cluster Extension connects the disk
array software with the cluster software, and uses the cluster software to react to system hardware
and application failures.
Servers are members of the same cluster dispersed over two or more sites.
XP Cluster Extension supports one-to-one and consolidated-site configurations.
One-to-one configurations
In one-to-one (1:1) configurations, cluster host nodes are split between two geographically separate
data centers and use redundant, diversely routed network connections for intra-cluster
communications. For an example of a one-to-one configuration, see “One-to-one (1:1) configuration”
(page 7). These links must be as reliable as possible to prevent false failover operations or
split-brain situations.
Figure 1 One-to-one (1:1) configuration
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.
Fast Failback using Continuous Access 7