During some testing I found that when a dump is already in progress to our filer's local tape library (one drive), another dump can be run. (Okay, so I as at home and thought that the previous dump would have finished.) Both dumps were apparently running, thinking that they were successfully writing to the same tape.
An mt status command run during this period showed that the drive was ready, but checking the status several times showed that writing was occurring (block numbers were changing). Also, the fileno number increased several more times than it should have.
The behaviour I would expect is that is a dump is already running, another attempt to dump to the tape would result in a device busy message. Did I witness one dump clobbering another?
The filer is an F740, the library is a Qualstar 6110, and Data OnTap is version 5.2.1.
Thanks for any insight.