HP 3PAR Cluster Extension Software Administrator Guide (5697-2047, June 2012)

NOTE: File Share Witness support:
• Windows Server 2003 (Service Pack 1 and later) supports only two node clusters when using
File Share Witness.
• Windows Server 2003 Service Pack 2 supports MNS with File Share Witness by default.
• When using Microsoft Windows Server 2003 Service Pack 1 (SP1)-based server cluster or
Windows Server 2003 R2-based server cluster, you must apply a Microsoft patch to support
MNS with File Share Witness. See your Microsoft documentation for more information.
SLE HA cluster setup considerations
Follow the guidelines in this section when you configure clusters for use with HP 3PAR Cluster
Extension.
Quorum
In an SLE HA cluster, quorum is defined as a strict majority of the defined cluster (more than 50%).
With certain failures, a cluster might be divided into two subclusters. In an SLE HA cluster, a
subcluster with more than 50% of the nodes wins the quorum. The subcluster that wins the quorum
re-forms the cluster and fences the subcluster that lost the quorum. The behavior of the subcluster
that lost the quorum depends on the defined no-quorum policy. This behavior is in effect until the
cluster is fenced. When the cluster is fenced, the resources owned by the fenced nodes fail over
to active cluster nodes.
STONITH
STONITH is an SLE HA cluster fencing method. SLE HA cluster provides STONITH plug-ins for
devices such as UPS, PDU, Blade power control devices, and lights out devices. Some plug-ins can
STONITH more than one node (for example, Split Brain Detector STONITH) and some can STONITH
only one node (for example, HP iLO STONITH).
HP iLO STONITH uses the power control functions of an HP iLO device to STONITH a node that
has lost quorum and needs to be fenced.
IMPORTANT: If all of the iLO devices in a cluster are connected using a single network, a single
switch failure might disable iLO, preventing nodes from being fenced. This failure might be difficult
to detect, especially before a node failure where iLO features would be required.
The STONITH action can be set to power off or reset, depending on the environment requirements.
• Power off: The STONITH agent powers off the nodes in the errant subcluster.
• Reset: The STONITH agent resets the nodes in the errant subcluster, and the nodes try to
automatically rejoin the cluster.
NOTE: IPMI fencing can be used for Integrity servers that do not support RIBCL scripting.
Networking in an SLE HA cluster
Configuring redundant and independent cluster communication paths is a good way to avoid Split
Brain conditions. With redundancy in communication paths, the loss of a single interface or switch
does not break the communication between nodes and prevents Split Brain conditions.
Administrators can configure multiple independent communication paths. HP recommends using
bonded Ethernet channels.
Resource constraints
Resource constraints allow administrators to specify which cluster nodes resources can run on, the
order resources are loaded, and the other resources a specific resource is dependent on.
Planning for HP 3PAR Cluster Extension 15