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

There are three types of resource constraints:
• Resource location: Defines the nodes on which a resource can run, cannot run, or is preferred
to be run.
• Resource colocation: Defines which resources can or cannot run together on a node.
• Resource order: Defines the sequence of actions for resources running on a node.
Resource operation attribute
SLE HA does not monitor resource health by default. To enable this feature, add the monitor
operation to the resource definition. You can specify the interval attribute and the timeout attribute
for a monitor operation. The interval attribute defines the time interval in which the monitor operation
is executed. The timeout attribute determines how long to wait before considering the resource as
failed.
Define start, stop, and monitor operations for the HP 3PAR Cluster Extension resource.
HP 3PAR Cluster Extension resource dependency
A Group resource in an SLE HA cluster ensures that the member resource agents are started and
stopped in the required order. A HP 3PAR Cluster Extension resource must be added as the first
member of the group. This way, all primitive resources added after the HP 3PAR Cluster Extension
resource are dependent on HP 3PAR Cluster Extension.
Since the primitive resources within a resource group can be failed over independently, set a
collocation constraint for each resource group ID with the last resource in the group to achieve the
failover of the entire group when any primitive resource fails.
Failover order
Use location constraints to define the failover order for a resource group.
For each node, define a location constraint with the appropriate score to prioritize the resource
group on that particular node. During failover, the cluster calculates the score of the resource group
on the available nodes, and the node with the highest score is considered the next preferred owner.
For more information, see the SLE HA documentation.
Failback option
HP does not recommend auto failback in configurations with HP 3PAR 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).
SLE HA provides the meta-attribute resource-stickiness to determine how much a resource agent
prefers to stay where it is. To disable auto failback, set resource-stickiness to the lowest value
compared to the other resource location constraints.
Migration-threshold
A resource is automatically restarted if it fails. If a restart cannot be achieved on the current node
or it fails to start a certain number of times on the current node, it tries to fail over to another node.
You can define the number of failures for resources (a migration-threshold) after which they migrate
to a new node. If you have more than two nodes in your cluster, the high availability software
chooses the node a particular resource fails over to.
When a HP 3PAR Cluster Extension resource fails, HP recommends configuring your cluster to fail
over the resource without restarting on the local node. To set this preference, set the
migration-threshold to 1.
16 HP 3PAR Cluster Extension features