# Automatic scaling for Amazon MSK clusters
To automatically expand your cluster's storage in response to increased usage, you can configure an Application Auto-Scaling policy for Amazon MSK. In an auto-scaling policy, you set the target disk utilization and the maximum scaling capacity.
Before you use automatic scaling for Amazon MSK, you should consider the following:
+
**Important**
A storage scaling action can occur only once every six hours.
We recommend that you start with a right-sized storage volume for your storage demands. For guidance on right-sizing your cluster, see [Right-size your cluster: Number of Standard brokers per cluster](bestpractices.md#brokers-per-cluster).
+ Amazon MSK does not reduce cluster storage in response to reduced usage. Amazon MSK does not support decreasing the size of storage volumes. If you need to reduce the size of your cluster storage, you must migrate your existing cluster to a cluster with smaller storage. For information about migrating a cluster, see [Migrate to MSK cluster](migration.md).
+ Amazon MSK doesn't support automatic scaling in the Asia Pacific (Osaka), Africa (Cape Town), and Asia Pacific (Malaysia) Regions.
+ When you associate an auto-scaling policy with your cluster, Amazon EC2 Auto Scaling automatically creates an Amazon CloudWatch alarm for target tracking. If you delete a cluster with an auto-scaling policy, this CloudWatch alarm persists. To delete the CloudWatch alarm, you should remove an auto-scaling policy from a cluster before you delete the cluster. To learn more about target tracking, see [Target tracking scaling policies for Amazon EC2 Auto Scaling](https://docs.aws.amazon.com/autoscaling/ec2/userguide/as-scaling-target-tracking.html) in the *Amazon EC2 Auto Scaling User Guide*.
**Topics**
+ [Auto-scaling policy details for Amazon MSK](msk-autoexpand-details.md)
+ [Set up automatic scaling for your Amazon MSK cluster](msk-autoexpand-setup.md)
# Auto-scaling policy details for Amazon MSK
An auto-scaling policy defines the following parameters for your cluster:
+ **Storage Utilization Target**: The storage utilization threshold that Amazon MSK uses to trigger an auto-scaling operation. You can set the utilization target between 10% and 80% of the current storage capacity. We recommend that you set the Storage Utilization Target between 50% and 60%.
+ **Maximum Storage Capacity**: The maximum scaling limit that Amazon MSK can set for your broker storage. You can set the maximum storage capacity up to 16 TiB per broker. For more information, see [Amazon MSK quota](limits.md).
When Amazon MSK detects that your `Maximum Disk Utilization` metric is equal to or greater than the `Storage Utilization Target` setting, it increases your storage capacity by an amount equal to the larger of two numbers: 10 GiB or 10% of current storage. For example, if you have 1000 GiB, that amount is 100 GiB. The service checks your storage utilization every minute. Further scaling operations continue to increase storage by an amount equal to the larger of two numbers: 10 GiB or 10% of current storage.
To determine if auto-scaling operations have occurred, use the [ ListClusterOperations](https://docs.aws.amazon.com/msk/1.0/apireference/clusters-clusterarn-operations.html#ListClusterOperations) operation.
# Set up automatic scaling for your Amazon MSK cluster
You can use the Amazon MSK console, the Amazon MSK API, or CloudFormation to implement automatic scaling for storage. CloudFormation support is available through [Application Auto Scaling](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-applicationautoscaling-scalabletarget.html).
**Note**
You can't implement automatic scaling when you create a cluster. You must first create the cluster, and then create and enable an auto-scaling policy for it. However, you can create the policy while Amazon MSK service creates your cluster.
**Topics**
+ [Set up automatic scaling using the Amazon MSK AWS Management Console](msk-autoexpand-setup-console.md)
+ [Set up automatic scaling using the CLI](msk-autoexpand-setup-cli.md)
+ [Set up automatic-scaling for Amazon MSK using the API](msk-autoexpand-setup-api.md)
# Set up automatic scaling using the Amazon MSK AWS Management Console
This process describes how to use the Amazon MSK console to implement automatic scaling for storage.
1. Sign in to the AWS Management Console, and open the Amazon MSK console at [https://console.aws.amazon.com/msk/home?region=us-east-1\$1/home/](https://console.aws.amazon.com/msk/home?region=us-east-1#/home/).
1. In the list of clusters, choose your cluster. This takes you to a page that lists details about the cluster.
1. In the **Auto scaling for storage** section, choose **Configure**.
1. Create and name an auto-scaling policy. Specify the storage utilization target, the maximum storage capacity, and the target metric.
1. Choose `Save changes`.
When you save and enable the new policy, the policy becomes active for the cluster. Amazon MSK then expands the cluster's storage when the storage utilization target is reached.
# Set up automatic scaling using the CLI
This process describes how to use the Amazon MSK CLI to implement automatic scaling for storage.
1. Use the [ RegisterScalableTarget](https://docs.aws.amazon.com/cli/latest/reference/application-autoscaling/#available-commands) command to register a storage utilization target.
1. Use the [ PutScalingPolicy](https://docs.aws.amazon.com/cli/latest/reference/application-autoscaling/#available-commands) command to create an auto-expansion policy.
# Set up automatic-scaling for Amazon MSK using the API
This process describes how to use the Amazon MSK API to implement automatic scaling for storage.
1. Use the [ RegisterScalableTarget](https://docs.aws.amazon.com/autoscaling/application/APIReference/API_RegisterScalableTarget.html) API to register a storage utilization target.
1. Use the [ PutScalingPolicy](https://docs.aws.amazon.com/autoscaling/application/APIReference/API_PutScalingPolicy.html) API to create an auto-expansion policy.