# Creating a custom CloudWatch alarm for your gateway
Creating a custom CloudWatch alarm

CloudWatch uses Amazon Simple Notification Service (Amazon SNS) to send alarm notifications when an alarm changes state. An alarm watches a single metric over a time period that you specify, and performs one or more actions based on the value of the metric relative to a given threshold over a number of time periods. The action is a notification that's sent to an Amazon SNS topic. You can create an Amazon SNS topic when you create a CloudWatch alarm. For more information about Amazon SNS, see [What is Amazon SNS?](https://docs.aws.amazon.com/sns/latest/dg/welcome.html) in the *Amazon Simple Notification Service Developer Guide*.

**To create a CloudWatch alarm in the Storage Gateway console**

1. Open the Storage Gateway console at [https://console.aws.amazon.com/storagegateway/home/](https://console.aws.amazon.com/storagegateway/home/).

1. In the navigation pane, choose **Gateways**, then choose the gateway for which you want to create an alarm.

1. On the gateway details page, choose the **Monitoring** tab.

1. Under **Alarms**, choose **Create alarm** to open the CloudWatch console.

1. Use the CloudWatch console to create the type of alarm that you want. You can create the following types of alarms:
   + Static threshold alarm: An alarm based on a set threshold for a chosen metric. The alarm enters the ALARM state when the metric breaches the threshold for a specified number of evaluation periods.

     To create a static threshold alarm, see [Creating a CloudWatch alarm based on a static threshold](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/ConsoleAlarms.html) in the *Amazon CloudWatch User Guide*.
   + Anomaly detection alarm: Anomaly detection mines past metric data and creates a model of expected values. You set a value for the anomaly detection threshold, and CloudWatch uses this threshold with the model to determine the "normal" range of values for the metric. A higher value for the threshold produces a thicker band of "normal" values. You can choose to activate the alarm only when the metric value is above the band of expected values, only when it's below the band, or when it's above or below the band.

     To create an anomaly detection alarm, see [Creating a CloudWatch alarm based on anomaly detection](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/Create_Anomaly_Detection_Alarm.html) in the *Amazon CloudWatch User Guide*.
   + Metric math expression alarm: An alarm based one or more metrics used in a math expression. You specify the expression, threshold, and evaluation periods.

     To create a metric math expression alarm, see [Creating a CloudWatch alarm based on a metric math expression](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/Create-alarm-on-metric-math-expression.html) in the *Amazon CloudWatch User Guide*.
   + Composite alarm: An alarm that determines its alarm state by watching the alarm states of other alarms. A composite alarm can help you reduce alarm noise.

     To create a composite alarm, see [Creating a composite alarm](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/Create_Composite_Alarm.html) in the *Amazon CloudWatch User Guide*.

1. After you create the alarm in the CloudWatch console, return to the Storage Gateway console. You can view the alarm by doing one of the following:
   + In the navigation pane, choose **Gateways**, then choose the gateway for which you want to view alarms. On the **Details** tab, under **Alarms**, choose **CloudWatch Alarms**.
   + In the navigation pane, choose **Gateways**, choose the gateway for which you want to view alarms, then choose the **Monitoring** tab.

     The **Alarms** section lists all of the CloudWatch alarms for a specific gateway. From here, you can select and delete one or more alarms, turn alarm actions on or off, and create new alarms.
   + In the navigation pane, choose **Gateways**, then choose the alarm state of the gateway for which you want to view alarms.

For information about how to edit or delete an alarm, see [Editing or deleting a CloudWatch alarm](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/Edit-CloudWatch-Alarm.html).

**Note**  
When you delete a gateway using the Storage Gateway console, all CloudWatch alarms associated with the gateway are also automatically deleted.