A common system metric to monitor is the available disk space on a given system or host. This guide helps you create a monitor that alerts you when free disk space for a host falls below 10% for any host reporting to Datadog.

To create the monitor for available disk space:

1. In the navigation menu, click Monitors.

2. Click New Monitor.

3. Select Metric as the monitor type.

   1. In the Define the metric section, use system.disk.free for the metric and select host for avg by. This is Query a.

   2. Click Add Query. For this metric, use system.disk.total for the metric and use host for avg by. This is Query b.

   3. In the formula that appears, replace a + b with a/b*100.

   4. Under Evaluation Details, choose your desired evaluation interval.

4. Under Set alert conditions, select below from the threshold options and enter 10 in Alert threshold field.

5. In Configure notifications & automations, give your monitor a name, then specify the notification message. Include relevant details and a meaningful message template. For example:

     {{#is_alert}}Warning: Free disk space is below 10% on {{host.name}}. Free space: {{system.disk.free}} bytes, Total space: {{system.disk.total}} bytes.{{/is_alert}}
   

6. Click Create to save the monitor.