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

Chapter 2: Introduction 11
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.
Event Notification
A notifier defines how the cluster handles state transition, error, warning,
and informational messages. You can configure a notifier with a
combination of events and originating cluster entities and then supply a
script that specifies the action the notifier should take. For example, you
could forward events to e-mail or to any other user-defined process.
Cluster Design Guidelines
Be sure to consider the following guidelines when planning the physical
configuration of your HP Clustered File System cluster.
Server Memory
Memory resources are consumed on each cluster server to manage the
state necessary to preserve the coherency of shared filesystems. For this
reason, the servers in the cluster should have approximately equal
amounts of physical memory. As a guideline, the ratio of memory
between the smallest and largest servers should not exceed 2. For
example, the smallest server could have 1 GB of memory and the largest
server 2 GB. If this ratio is exceeded (such as a 256 MB server and a 2 GB
server, with a ratio of 8), paging can increase on the smallest server to the
extent that overall cluster performance is significantly reduced.