4.1.0 HP PolyServe Matrix Server administration guide (T5392-96073, October 2010)

When the health of one of these servers is equal to or greater than the backup server
where the virtual host currently resides, the virtual host automatically attempts to fail
over to that server.
NOFAILBACK
NOFAILBACK is intended to minimize failovers. The virtual host remains active on
the backup server until a healthier server (it’s health is greater than the backup server)
becomes available, at which point the virtual host will fail over to that server.
For example, consider a two-node cluster that is configured with its primary on node
1 and backup on node 2, and that uses the NOFAILBACK option. Three service
monitors are configured on the virtual host. When a service monitor probe fails on
node 1, the virtual host will fail over to node 2. Following are some possible failback
scenarios:
• When the monitored service is restored on node 1, the virtual host will remain
on node 2. Node 1 and node 2 are equally healthy; they both have three up
service monitors. The NOFAILBACK policy will not move the virtual host until a
healthier server is available.
• After the virtual host fails over to node 2, a service monitor probe fails on that
node. Now both nodes have a down service monitor. Failback does not occur
because the servers are equally healthy. If the failed service is then restored on
node 1, that node will now be healthier than node 2 and failback will occur.
(Note that if the virtual host policy was AUTOFAILBACK, failback would occur
when the probe failed on node 2 because both servers were equally healthy.)
• After the virtual host fails over to node 2, all service monitor probes fail on that
node. Node 1, with one down monitor, is now healthier than node 2, with three
down monitors, and failback will occur.
Failback policy and monitor probe severity
The following table shows how the virtual host failback policy interacts with the probe
severity setting for service and device monitors.
Behavior when Probe Reports DOWN
Monitor Probe
Severity
Virtual Host
Policy
Failover does not occur.NOFAILOVERAUTOFAILBACK
Failover occurs. When service is restored, fail-
back occurs.
AUTORECOVER
Configure virtual hosts200