HP EVA Cluster Extension Software Installation Guide (5697-2446, July 2013)

Failover function
HP EVA Cluster Extension Software requires cluster software to automatically fail over among
systems on a local site or between sites. Because the software manipulates the application startup
process before storage system vdisks are accessed, it must be integrated as the first resource (in
the order of resources). The software must be installed on all servers in the cluster that can run the
application service.
How HP EVA Cluster Extension utilizes vdisks
To write to the EVA Continuous Access paired vdisks, you must ensure that the paired vdisks are
in read/write mode. DR group members (paired vdisks) are only in read/write mode on the source
(primary) vdisk. The destination (secondary) vdisk is in read-only mode.
• In case of a failover, the HP EVA Cluster Extension Software automatically changes the direction
of the mirrored pair. A reboot of the server is not necessary.
• In case of a disaster, the storage system can have several different states for DR group members.
HP EVA Cluster Extension Software determines whether those vdisks can be accessed and
made available to the application service.
How HP EVA Cluster Extension stores information
HP EVA Cluster Extension stores information about the application environment in an internal object
database and uses HP EVA SMI-S to gather information about the state of the associated DR group
members. Information about the configured storage system environment and failover behavior is
transferred either directly by the cluster software or by gathering it from the user configuration file.
An internal object database provides the software with the format and default value of supported
parameters.
Vdisk states are stored in the internal object database, that uses a rule engine to process the DR
group member states. The rule engine matches current DR group member states and configuration
parameters with a defined rule, stores it in the database, and invokes predefined actions. Those
actions prepare the DR group member vdisks to be enabled for access or stop the application
service startup process if the matching rule requires a stop.
General installation prerequisites
This section describes general installation prerequisites for the HP EVA Cluster Extension.
Environmental setup
Ensure that the following conditions are met before installing HP EVA Cluster Extension Software:
• EVA Continuous Access links (including extender hardware) are redundant and bidirectional.
• Alternate I/O paths between servers and the EVA storage system are set up.
• Cluster and client networks are redundant.
• Cluster nodes can communicate with each other.
• The latest supported software and firmware versions, fixes, FC adapter firmware, and driver
versions for your servers and EVA storage systems are installed.
• The cluster nodes in your zoning configuration each recognize their respective (local) EVA
array, but not the remote EVA array. Each management server recognizes both EVA arrays
and can recognize each other.Figure 1 (page 7) shows a zoning example.
6 Preparing to install HP EVA Cluster Extension