HP Storage Mirroring V5.1 Software - Manual (Page 124)

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11. If you are monitoring multiple IP addresses, highlight the source name and specify the Failover
Trigger.

All Monitored IP Addresses Fail—Failover begins when all monitored IP addresses fail. If
there are multiple, redundant paths to a server, losing one probably means an isolated
network problem and you should wait for all IP addresses to fail.

One Monitored IP Address Fails—Failover begins when any one of the monitored IP
addresses fails. If each IP address is on a different subnet, you may want to trigger failover
after one fails.
12. If Manual Intervention is enabled, Target Data State at Failover will be disabled because
the same options will be presented to you at failover time. If Manual Intervention is disabled,
the options will be enabled so that an option can be selected to occur automatically when failover
occurs. Highlight the source name and specify the Target Data State at Failover by specifying
what data you want to use on the target when failover occurs.

Apply Data in Target Queues Then Failover—All of the data in the target queue will be
applied before failover begins. Depending on the amount of data in queue, the amount of time
to apply all of the data could be lengthy.

Discard Data in Target Queues and Failover Immediately—All of the data in the target
queue will be discarded and failover will begin immediately. Any data in the target queue will
be lost.

Revert to Last Good Snapshot if Target Data is Bad—If the target data is in a bad Storage
Mirroring state, Storage Mirroring will automatically revert to the last good Storage Mirroring
snapshot before failover begins. You will lose any data between the last good snapshot and
the failure. If the target data is in a good state, Storage Mirroring will not revert the target
data. Instead, Storage Mirroring will apply the data in the target queue and then failover.
Depending on the amount of data in queue, the amount of time to apply all of the data could
be lengthy.
13. Highlight the source name and specify the Items to Failover, which identifies which source
components you want to failover to the target.

IP Addresses—If you want to failover the IP addresses on the source, enable this option and
then specify the addresses that you want to failover.

Monitored—Only the IP address(es) that are selected for monitoring will be failed over.

All—All of the IP address(es) will be failed over.
NOTE: If you are monitoring multiple IP addresses, IP address conflicts may occur during
failover when the number of IP addresses that trigger failover is less than the
number of IP addresses that are assumed by the target during failover. For
example, if a source has four IP addresses (three public and one private), and two
of the three public addresses are monitored, but all three public addresses are
configured to failover, a conflict could occur. If the source fails, there is no conflict
because all of the IP addresses have failed and no longer exist. But if the failure
only occurs on one of the monitored addresses, the other two IP addresses are
still affected. If all of the addresses are failed over, these addresses then exist on
both the source and the target. Therefore, when a source machine has fewer IP
addresses that trigger failover than IP addresses that will be failed over, there is
a risk of an IP address conflict.
If your network environment is a WAN configuration, do not failover your IP
addresses unless you have a VPN infrastrucutre so that the source and target can
be on the same subnet, in which case IP address failover will work the same as a
LAN configuration. If you do not have a VPN, you can automatically reconfigure
the routers via a failover script (by moving the source's subnet from the source's
physical network to the target's physical network). There are a number of issues
to consider when designing a solution that requires router configuration to achieve
IP address failover. Since the route to the source's subnet will be changed at
failover, the source server must be the only system on that subnet, which in turn
requires all server communications to pass through a router. Additionally, it may
take several minutes or even hours for routing tables on other routers throughout
the network to converge.