If the number of online drives in the library does not match the number of online paths to drives in the library for any applicable source, it might cause the server to choose a drive that lacks a valid path definition. The server will then retry the mount operation and any retry could adversely affect mount performance.
The operation continues, but receiving this message indicates that there might be a possible mount retry if the selected drive does not have a valid, online path defined.
Evaluate all drive path definitions. Define drive paths for any drives that lack a path definition for any applicable source (for example storage agents). Validate that all drive path definitions are online. If a drive path is offline for a hardware reason, resolve the hardware issue and update the path so that it is back online.