HP StorageWorks Continuous Access EVA Administrator Guide (T3687-96043, December 2005)

3Failoverandrecovery
This chapter provides information for failing over and resuming operations after a planned or unplanned
loss of operation. Several scenarios cover most situations you could enc ounter, with procedures for
handling each scenario.
Planning for a
disaster
Planning hel
ps minimize the downtime brought on by a disaster. Include the following in your disaster
recovery planning:
• Operate with a suppor ted disaster-tolerant configuration. Ensure that there are two fabrics with
one interswitch link per fabric or, in extended SANs, an intersite link for each fabric.
• Ensure that
array controllers are cabled in the suppor ted configuration.
• H ave at least one management server available at every site, in case of a hardware or
communication failure.
• Verify that each destination virtual disk within a DR group has been presented to a host. This
allows the host access to the virtual disk immediately a fter a failover.
• Ensure th
at local and remote hosts are installed with the latest patches, virus protection, HP
Storage System Scripting Utility, and multipath software versions for the specific operating system.
• Keep your configuration current and documented at all sites. Install the latest versions of controller
software, HP Command View EVA, and the replication manager. Consider replicating the boot
disks of all servers attached to the array.
• Keepare
cord of your virtual disks, D R groups, and host volume and volume group names.
Captur
etheconfiguration informatio n after each significant change or at scheduled intervals
(see Ba
cking up replication configuration).
• Keep the replication manager on every management server synchronized with configuration
changes. See the replication manager online help for the procedure to export and import the
replication mana ger database.
• Back u
p the replication manager database. These databases contain managed set and job
info
rmation that you can restore on another management server if its role changes.
• Practice the recovery plan. Ensure that everyone in your storage administration practices for
disaster recovery. Practice different failure scenarios and make decisions ahead of time about
them. For example, if a controller fails, is it more important not to disrupt processing by doing a
plannedfailover,ornottobeatriskforasecondcontroller failure that will result in an unplanned
fai
lover? In the case of multiple sites, which site has precedence for troubleshooting? Simulated
dis
aster recoveries are a good way to verify that your records are up-to-date and that all required
patches are installed.
Failover and recovery procedures
The failover procedure depends on the severity of the failure or the reason for the failover. For example,
the procedure for a planned failover applies to anticipated power disruptions, scheduled equipment
maintenance at the local site, or a need to transfe r operations to another array. Another procedure
applies to unplanned events such as multiple controller failures, multiple host failures, or a power outage
at the local site.
You may decide not to fail over in some situations. For example, if only one component fails, you may
be able to repair that component and avoid failing over an entire DR group. On the other hand, if a
local array fails, or if you are planning downtime with a local array, failing over to the remote array
can ensure minimal interruption of data access.
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