HP Tru64 UNIX and TruCluster Server Version 5.1.B-4 Patch Summary and Release Notes (13156)

A Setting Up an Enhanced Distance Cluster
An Enhanced Distance Cluster allows a cluster to be extended between two sites up to 100 km
apart to assist recovery in the event of a disaster. An Enhanced Distance Cluster provides basic
high availability services in the event of the loss of a single component. It is important to note
that an Enhanced Distance Cluster is not designed to handle nor is it capable of handling
simultaneous cascading failures and therefore can not provide a fully disaster tolerant solution.
The following topics are discussed:
• The section “Enhanced Distance Cluster Configuration Requirements” lists configurations,
features, and functions that must be present in order to have a supported Enhanced Distance
Cluster configuration.
• The section “Enhanced Distance Cluster Restrictions” (page 184) lists configurations, features,
and functions that cannot be present in order to have a supported Enhanced Distance Cluster
configuration.
• The section “Enhanced Distance Cluster Recommendations” (page 185) lists configurations,
features, functions that should be present, but are not required to have a working Enhanced
Distance Cluster.
A.1 Enhanced Distance Cluster Configuration Requirements
This section provides information on the hardware and configurations supported for Enhanced
Distance Clusters. Configurations that deviate from these configurations will require a custom
support statement from Hewlett Packard in order to be supported. See the TruCluster Server
QuickSpecs for information on hardware components supported by the TruCluster Server
product.
The following table lists supported hardware.
Table A-1 Hardware Configuration
2 to 4 nodesNumber of Nodes
Any node supported in a TruCluster configuration.CPU Type
Any Fibre Channel HBA supported by TruCluster. (Parallel SCSI is not supported for any
storage that can potentially fail over between locations.)
Fibre Channel Adapter
(HBA)
Gigabit Ethernet LAN with up to three switches. Cumulative distance must not exceed 100
km.
Interconnect
TruCluster Fibre Channel connected storage (such as HP StorageWorks XP and HP
StorageWorks EVA).
Storage
The following list describes configuration requirements for the cluster:
• A two- to four-node cluster with up to three nodes at one site and the other nodes at a
different site. (See Figure A-1.)
• The cluster must be configured as a LAN cluster.
• A least one shared storage array must be present at each site.
• The cluster root (/), /usr, and /var file systems must be located within the same site.
• All SAN-attached storage must be shared and directly accessible — not over the cluster
inter-site connection but via the SAN — from all nodes at both sites.
• The storage must be configured with remote data replication software (such as XP Continuous
Access). Data replication is required in order to provide the ability to boot the site that does
not contain the cluster file systems following a disaster event.
• A reboot of all nodes at the surviving site is required following any disaster event that
requires activation of the secondary replicated volumes. You will need to shut down the
system, reconfigure the storage as necessary (perform an XP takeover, for example), and
reboot the system. The expected quorum votes and other parameters may need to be modified
in order to successfully boot the system.
A.1 Enhanced Distance Cluster Configuration Requirements 183