HP StorageWorks Clustered File System 3.6.0 Windows Storage Server Edition Administration Guide (403103-005, January 2008)

Chapter 18: Advanced Monitor Topics 229
Custom Device Monitors
A custom device monitor is associated with a list of servers and a list of
virtual hosts configured on those servers. A custom device monitor can
be active on only one server at a time. On each server, the monitor uses a
probe mechanism to determine whether the service is active. The probe
mechanism is in one of the following states on each server: Up, Down,
Unknown, Timeout.
A custom device monitor also has an activity status on each server. This
status indicates the current activity of the monitor on the server. The
status can be one of the following: Starting, Active, Suspended, Stopping,
Inactive, Failure.
If it is necessary to fail over a virtual host associated with the custom
device monitor, HP Clustered File System looks for a server that meets
both of these conditions: the device monitor is active, and the device
monitor probe reports an Up status. If HP Clustered File System cannot
locate a server where the device is active and the probe status is Up, the
virtual host will be left inactive across the cluster.
The following example shows the state transitions for a custom device
monitor and its associated virtual host. The device monitor uses the
default values for autorecover, priority, and serial script ordering, and has
a Start and Stop script defined. The virtual host is configured with a
Primary network interface and two backup interfaces. There is also a
service monitor defined on the virtual host. It uses the default values for
autorecovery, priority, and serial script ordering and has Start and Stop
scripts defined.
The example begins at initial startup from an unknown state and the
virtual host is then located on the primary interface.
At time t1, the service monitor probe on the Primary reports a Down
status. The virtual host then becomes inactive all servers.
The virtual host cannot be active on the Primary server because the
service monitor is Down. It cannot become active on either of the backup
servers because the custom device monitor associated with the virtual
host is Inactive on these servers.