HP Cluster Software manual Preparing to install HP 3PAR Cluster Extension, Ideal environment

1 Preparing to install HP 3PAR 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 a pair of HP 3PAR storage system with Remote Copy configuration. 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 HP 3PAR Cluster Extension, note the following:

•Network communications links and components between the dispersed data centers must be redundant 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 communication links 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.

•Multi-pathing software must be used for host-to-storage connections.

Storage replication link requirements

To ensure reliable data backup between the local (primary) and remote (secondary) storage systems, at least two HP 3PAR Remote Copy 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 HP 3PAR Remote Copy links.

Server cluster infrastructure requirements

Use two cluster nodes 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.

For windows, using a Node Majority quorum requires an odd number of cluster nodes, with at least one system in a third location. Where as, using a Node Majority with file share witness requires even number of cluster nodes at each site with file share witness server at the third location.

CAUTION: HP 3PAR Cluster Extension works with one server at each location, with a single I/O path between the server and storage system, and a single link between storage systems. However, any configuration with a single point of failure is not considered highly available or disaster tolerant. HP does not support configurations with single points of failure; configurations with one system at each location are supported only if there are no single points of failure.

How HP 3PAR Cluster Extension Software interacts with its environment

This section describes the ways in which HP 3PAR Cluster Extension interacts with its environment.

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