Backups to a storage device fail with the following error message:

Disk storage is down (2106)

The storage server is an OpenStorage (OST) host, and the Master Server and Media Server are both acting as Media Servers under Credentials > Storage Servers in the Administration Console. The disk pool is in an Up state and the storage server is in a Down state. Troubleshooting confirmed the OST plug-ins on the servers are mismatched.

Which command should an administrator use to check the plug-in version installed on the servers?