EBS volumes are deleted on termination by default.  To make them persist, you need to flag them with Persistent=true in the cluster template.  

If the cluster has already been started, follow these steps:

  1. Add the Persistent=true flag to the cluster template and re-import with the --force option.

  2. Change the DeleteOnTermination flag in AWS for the instance:

    $ aws ec2 modify-instance-attribute --instance-id <instance_id> --block-device-mappings "[{\"DeviceName\": \"/dev/sdb\",\"Ebs\":{\"DeleteOnTermination\":false}}]"


Make sure to replace <instance_id> with the actual instance ID of the running instance the volume is attached to.