HP StorageWorks EVA Cluster Extension Software Administrator Guide (T3667-96045, April 2010)

Recovery policy
When a resource inside the service fails, the default action is to restart the service on the local node
before the failover. In an EVA Cluster Extension environment, it is always expected to relocate the
service during restart. To enable this functionality, set the service recovery policy to relocate.
Service hierarchical structure and resource dependency
In RHCS, a service is a collection of cluster resources configured into a single entity that is managed
(started, stopped, or relocated) for high availability. A service is represented as a resource tree that
specifies each resource, its attributes, and its relationship among other resources in the resource tree.
The relationships can be parent, child, or sibling. Even though a service is seen as a single entity, the
hierarchy of the resources determines the order in which each resource within the service is started
and stopped.
In the case of a child-parent relationship, the startup or shutdown is simple. All parents are started
before children, and children must all stop cleanly before a parent can be stopped. For a resource
to be considered in good health, all of its children must be in good health.
A service is considered failed if any of its resources fail. In this case, the expected course of action
is to restart the entire service, including the failed resource and the other resources that did not fail.
In an EVA Cluster Extension environment, configure the EVA Cluster Extension resource as the parent
resource in the service so that EVA Cluster Extension can control the service behavior based on the
user configuration and storage device status. This means that the EVA Cluster Extension resource must
be configured at the highest level in the dependency hierarchy.
Disk monitoring
For the situations in which disk access is lost or read/write protection is in effect due to storage fencing,
application monitoring agents, file system agents, or LVM resource agents detect the IO failure. EVA
Cluster Extension does not monitor the disk access status.
Storage system configurations
Cluster configurations typically consist of two or more server systems connected to a shared storage
system. EVA Cluster Extension allows the dispersion of data center resources by enabling cluster
systems to take advantage of EVA storage systems configured for Continuous Access EVA operations.
EVA Cluster Extension connects the EVA management software used to control EVA storage systems
(and Continuous Access EVA) with the cluster software and uses the cluster software to react to system
hardware and application failures.
EVA Cluster Extension behavior is based on four major considerations:
• Cluster software failover behaviors
• EVA Cluster Extension user settings
• The replication mode setting for Continuous Access EVA, which is used to configure the remote
replication feature of an EVA storage system environment based on your needs for application
service availability, data concurrency, and replication performance
• DR group member status information
EVA Cluster Extension supports one-to-one and consolidated DR site configurations.
EVA Cluster Extension features16