HP StorageWorks Clustered File System 3.2.1 Windows Storage Server Edition Administration Guide (February 2006)

Chapter 12: Configure Device Monitors 122
Failover
If a probe of a monitored device fails, HP Clustered File System attempts
to relocate any virtual hosts that depend on the monitored device to a
healthier server. A virtual host is never active on a server with an
inactive, down, or disabled monitored device. If every server configured
for a virtual host has a down device that the virtual host depends on, the
virtual host will not be active anywhere in the cluster and thus will be
totally down.
When a
DISK monitor is used to check access to a SAN partition, the
probe can fail because of a problem with the server or with the disk itself.
If the monitor probe succeeds on another server assigned to the monitor,
HP Clustered File System can fail over the associated virtual hosts to that
server. The applications controlled by the virtual hosts will then be active
on that server and access to the filesystem will continue.
Device Monitors and Failover
When you create a device monitor, you specify a list of servers on which
the device monitor will operate. The servers are placed in order: primary,
backup #1, backup #2, and so on. ClusterPulse considers the status and
enablement of the servers when determining where to activate a monitor.
Device Monitor Activeness Policy
ClusterPulse uses the following device monitor activeness policy to
determine the server or servers where it will make a device monitor
active. The policy described here is accurate for this release but it may
change in future releases.
The device monitor activeness policy decision is made as follows:
1. If the device monitor on a specific server is disabled, then the device
monitor will not be made active on that server.
2. ClusterPulse considers the list of servers that are both up and enabled
and that are configured for the device monitor. Note the following:
• A server that has not finished joining the cluster (see “Server
Access to the SAN” on page 156) is not considered up for the
purpose of activating the device monitor.