This example scenario demonstrates a type of alarm action that you configure for an object in the vSphere inventory, including responding to the alarm when it triggers. This example demonstrates how to modify the Datastore usage on disk alarm to send emails when certain thresholds are reached, and describes how to respond to the alarm when it is triggered. You are the administrator of a small vSphere environment. You configure alarms to monitor the datastore usage on one of your hosts, named ESXi-A. ESXi-A is managed by the vCenter Server system My vCenter Server 5.1.

With thin provisioning, it is possible to oversubscribe storage space if the virtual machines grow unattended. An alarm set on the datastore can notify you when the space issues threaten to become critical.

Dozens of default alarm definitions are provided by the vSphere Web Client, which you can locate in the Manage tab for an inventory object. One of these default alarms is Datastore usage on disk, which you use to monitor the percentage of disk usage. This kind of alarm is important if the virtual machines in the datastore have virtual disks in the thin provisioned format. At first, a thin provisioned disk uses only as much datastore space as the disk initially needs. However, if the thin disk needs more space, it can grow to the maximum capacity allocated to it.

To configure alarms to send email notifications, you must have a running SMTP server on your network.


VMware recommends that you first experiment with the procedures presented in vSphere Examples and Scenarios on test instances in your datacenter.

To configure alarm conditions and alarm actions for your vSphere environment, you can either create an alarm definition or edit an existing one. In this example, you use an existing alarm definition. Default alarms are not preconfigured with actions. You must manually set what action occurs when the triggering event, condition, or state occurs.

Alarm Definition Workflows
Workflow for alarms

You must have the Administrator role to configure alarms. Alarm privileges do not appear in other default sample roles accessible with the vSphere Web Client. To create a unique role for this process that does not include all the privileges of an Administrator, the following list contains the minimum privileges necessary.

Alarms.Create alarm

Alarms.Modify alarm

Alarms.Acknowledge alarm

For information about roles, permissions, and privileges, see the vSphere Security documentation.