I updated the storage size of my Amazon Relational Database (Amazon RDS) DB instance. But, the process is taking a long time, and the instance is in storage-optimization state.
When you modify the storage size of your Amazon RDS DB instance, the status of the instance changes to storage optimization. This means that your DB instance is being modified to change the storage size or type. The storage optimization process is performed by RDS automation. RDS automation confirms that the data is evenly distributed to the underlying Amazon Elastic Block Store (Amazon EBS) volumes after storage modification.
In most cases, scaling storage doesn't cause any outage or performance degradation of the DB instance. However, this operation might take several hours. You can't make further storage modifications for either six hours or until storage optimization has completed on the instance, whichever is longer. But, you can perform any other instance modifications like instance size scaling or rebooting.
Typically, the storage optimization completes in a few hours and can sometimes take up to and beyond 24 hours. When the DB instance is in the storage-optimization status, the instance is operational. Your application availability isn't affected. You don't have to wait for the DB instance to be in Available state to run your applications.
Note: There is no way to speed up this process— you must wait for the optimization process to complete. The larger the storage size increase, the larger the storage usage, and the longer the process takes. Because this is an automated process, there is no fixed way to determine how long it takes to complete storage-optimization on your RDS DB instance.
Because Amazon Aurora uses a customer storage solution that isn't backed by EBS volumes, you don't need to consider storage-optimization for Aurora instances. For more information, see Introducing the Aurora storage engine.
Note: Any type of storage modification can result in the DB instance moving to storage optimization status. But, modifying the storage might also cause the instance to restart, which requires some downtime. This is required in specific cases, such as changing the storage type from SSD to magnetic or vice versa. For more information, see Settings for DB instances.
To monitor the amount of free storage for your DB instance and action when necessary, it's a best practice to create an Amazon CloudWatch alarm.
Managing an Amazon RDS DB instance