In a vSphere environment, there are conditions (such as datastores running out of space) that you want to know about before things run out of control. In the "datastores running out of space" example, you would want to be warned before the datastore is full, so you can move some disks to another datastore to create extra free space on the datastore that is running out of space.

VMware vSphere provides alarms that trigger warnings and alerts when certain conditions are met. There are a lot of predefined alarms for almost every condition possible in vCenter Server. For example, there is the Datastore usage on disk alarm for datastores that will, by default, give you a warning if a datastore usage is above 75 percent and give you an alert if a datastore usage is above 85 percent. It is also possible to define actions such as Send a notification email that are executed when an alarm is triggered.

In PowerCLI, there are various cmdlets to modify alarm definitions and to create...