Amazon EBS supports increasing a volume size, but it does not support shrinking one directly. For a data volume, create a smaller volume and copy the files to it. A Windows root volume, or a data volume containing continuously written files such as SQL Server databases, should be handled offline after stopping the instance.

This example uses Windows Server 2012 R2. The original root and data volumes are both 100 GB gp3 volumes, and the target size is 50 GB each.

Create an AMI before starting, test the procedure in a non-production environment, and schedule the root-volume migration during a maintenance window. Stopping an instance can lose instance-store data and an automatically assigned public IP address (an Elastic IP is not affected).