HP XP Cluster Extension Software Administrator Guide

1 XP Cluster Extension features
HP XP Cluster Extension Software monitors XP Continuous Access disk pairs and enables automatic
access to remote data copies when clustered applications become unavailable locally. XP Cluster
Extension integrates with popular cluster software to ensure that consistent and concurrent data
copies on HP disk arrays can be accessed when needed.
Integration into cluster software
XP Cluster Extension integrates with Microsoft Failover Cluster (MSFC).
Integrating XP Cluster Extension with cluster software allows you to manage a disk array as if it
were a disk or volume group of the clustered application.
For supported cluster software versions, see the HP SPOCK website: http://www.hp.com/storage/
spock.
Enhanced disaster tolerance
The Continuous Access software copies valuable data to a remote data center so that you can
restore application service after a local server, storage, or data center failure. Disk arrays with
Continuous Access can change mirroring direction, swapping the primary/secondary relationship
of disk pairs almost instantaneously if the application must access the secondary disk. This feature
ensures that the failback process is as fast as the failover process. If the links between your primary
and secondary disk arrays are broken, each array maintains a bitmap table to synchronize the
changes when the links become available again.
Because cluster software requires the application service to have read/write access to data disks
and because the secondary volume of a Continuous Access disk pair is normally read-only, the
failover process using cluster software alone typically involves manual intervention. With XP Cluster
Extension Software, manual intervention is required only if the current disk array states and user
settings conflict with the rules stored in the XP Cluster Extension database.
Automated monitoring and redirecting of Continuous Access pairs
XP Cluster Extension monitors the health of the Continuous Access links between your arrays. When
it detects a lost and later re-established link, it automatically resynchronizes the suspended disk
pairs, ensuring that the most current data is available on either site. For information on configuring
resynchronization parameters, see “Monitoring and resynchronizing device/copy groups”
(page 61).
Rolling disaster protection
A rolling disaster is a catastrophic event that affects the remote site after an outage at the local
site. In a rolling disaster, data stored on remote disks can be entirely lost during a recovery attempt.
To ensure the survival of critical data during a resynchronization/restore operation, XP Business
Copy pairs can be associated with the local data disks. XP Cluster Extension recovers automatically,
provided that a local Business Copy mirror can be suspended.
Although the local copy can be out of date, it represents the best starting point for the recovery.
XP Cluster Extension also resumes local Business Copy mirrors automatically, if specified, to allow
the local site to keep an up-to-date image of the primary data. To implement rolling disaster
protection, see “Implementing rolling disaster protection” (page 59).
Command-line interface (CLI)
XP Cluster Extension Software provides a CLI to enable disaster tolerance without cluster software.
The CLI is convenient if you use in-house software to migrate application services from one system
6 XP Cluster Extension features