HP P6000 Cluster Extension Software Installation Guide (5697-0987, June 2011)

1 Preparing to install P6000 Cluster
Extension
This chapter provides information about general environment considerations and pre-installation
requirements.
Ideal environment
The ideal configuration environment consists of at least five servers (two at each data center site and
one as an arbitrator at a third site) with separate, redundant communications links for cluster heartbeats,
client access, and HP P6000 Continuous Access. All communications interfaces must be installed in
pairs to serve as failover components, in order to prevent single points of failure.
Network communication requirements
When using P6000 Cluster Extension, note the following:
• Network communications links and components between the dispersed data centers must be re-
dundant and physically routed differently to prevent the backhoe issue that is created when all
links between data centers are cut together. This redundancy and routing is especially important
to prevent the split-brain syndrome that occurs when systems in both data centers form new clusters
and allow access to both copies of the data. Using redundant and separately routed communications
and components, you can configure the failover behavior so that the application service startup
procedure stops if none of the remote cluster members can be reached.
• Alternative pathing software such as HP Secure Path for Windows operating systems must be used
for host-to-storage connections.
• Linux clusters might have specific network latency requirements. For more information, see the SLE
HA and RHCS documentation.
Data backup requirements
To ensure reliable data backup between the local (primary) and remote (secondary) storage systems,
at least two P6000 Continuous Access links must be available when the storage systems are connected
to provide redundancy and protection against single points of failure. Although communications links
can cover considerable distances, each network segment must be extended to the dispersed data
center to maintain a heartbeat among all servers. For extended distances, you must purchase extender
components to bundle the P6000 Continuous Access links.
Recommendation
Use two systems at each site to give local application service failover procedures among local cluster
systems priority over remote, more time-consuming failover procedures. When failing over, the software
must reconfigure the storage systems to change the mirroring direction. At the remote site, two systems
should be available in case the primary failover system experiences a hardware or power failure.
HP P6000 Cluster Extension Software Installation Guide 7