HP StorageWorks Storage Mirroring Recover User's Guide (T5437-96008, November 2009)

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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 infrastructure 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.
● Server Name—Failover is performed on the server name. If you specify the
server name to be failed over, first Storage Mirroring Recover checks the
hosts file and uses the first name there. If there is no hosts file, Storage
Mirroring Recover uses the first name in DNS. (Although, the first name in
DNS may not always be the same each time the DNS server is rebooted.)
Lastly, if there is no DNS server, Storage Mirroring Recover uses the Failover
Control Center monitor name.
● Shares—Failover is performed on shares.