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

Chapter 3: Introduction to HP Clustered File System 13
If any of these health checks fail, HP Clustered File System can transfer
the virtual host to a backup server and the network traffic will continue.
After creating virtual hosts, you will need to configure your network
applications to recognize them. When clients want to access a network
application, they use the virtual host address instead of the address of the
server where the application is running.
Service and Device Monitors
A service is a network service such as HTTP or FTP that is installed and
configured on the servers in the cluster. HP Clustered File System can be
configured to watch specific services with service monitors.
A service monitor is created on a virtual host. The service being
monitored should be installed on all servers associated with that virtual
host. When a service monitor determines that a service has failed, HP
Clustered File System transfers the virtual host for that service to a
backup server. For example, if the HTTP service fails, HP Clustered File
System will transfer the HTTP traffic to a backup server that provides
HTTP.
HP Clustered File System includes several built-in service monitors for
monitoring well-known network services. You can also configure custom
monitors for other services.
A device monitor is similar to a service monitor; however, it is assigned to
one or more servers. HP Clustered File System provides several built-in
device monitors. The
DISK device monitor can be used to watch local disk
drives or to check access to a partition on a SAN disk. The
GATEWAY
device monitor watches gateway devices. You can also define your own
custom device monitors.
By default, when a device monitor is assigned to a server, all virtual hosts
on that server are dependent on the device monitor. However, you can
select the virtual hosts that will be dependent on the device monitor. If a
device monitor indicates that a device is not functioning properly on the
primary server, HP Clustered File System transfers the dependent virtual
host addresses from the primary server to a backup server.