HP P6000 Cluster Extension Software Administrator Guide (5697-0986, June 2011)

• The HP iLO of each cluster system must be accessible over the network from every other cluster
system.
To handle infrequent failures of the HP iLO fencing (such as a switch failure), you can set up a backup
fence method for redundancy.
HP iLO fencing can be used on HP Proliant systems with built-in iLO hardware. For third-party systems,
other power control fencing methods can be used.
NOTE:
IPMI fencing can be used for Integrity servers that do not support RIBCL scripting.
Qdisk configuration
Red Hat recommends the use of a Qdisk configuration to bolster quorum to handle failures such as
half (or more) of the members failing, a tie-breaker in equal split partition, and a SAN failure.
In a P6000 Cluster Extension configuration with multiple storage arrays, a Qdisk configuration is not
supported.
Failover domains
A cluster service is associated with a failover domain, which is a subset of cluster nodes that are
eligible to run a particular cluster service. To maintain data integrity, each cluster service can run on
only one cluster node at a time. By assigning a cluster service to a restricted failover domain, you
can limit the nodes that are eligible to run a cluster service in the event of a failover, and you can
order the nodes by preference to ensure that a particular node runs the cluster service (as long as that
node is active).
A failover domain can have the following characteristics:
• Unrestricted: Specifies that the subset of members is preferred, but the cluster service assigned to
this domain can run on any available member.
• Restricted: The cluster service is allowed to run only on a subset of failover domain members.
• Unordered: The member on which the cluster service runs is chosen from the available list of failover
domain members with no preference order.
• Ordered: The failover domain member on which the cluster service runs is selected based on
preference order. The member at the top of the list (as specified in /etc/cluster/
cluster.conf) is the most preferred, followed by the second member, and so on.
For an orderly failover, HP recommends using the Ordered and Restricted options for your failover
domains.
Failback policy
HP does not recommend auto failback in configurations with P6000 Cluster Extension because the
resource failovers due to storage failure can cause resources to go into an unstable state
(failover/failback might toggle the resource between the nodes). In this situation, HP recommends
correcting the failure and then manually failing back to the intended data center or server.
To disable the auto failback, set the nofailback flag for the failover domain.
Enabling this option for an ordered failover domain prevents automated failback after a more-preferred
node rejoins the cluster.
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