We have this issue going where Veeam intermittentaly will not complete a full archive with the allotted tapes. We typically only need 5 - 5 1/2 tapes. Veeam will write to the tapes but then not see anything was written to the tapes and continually ask for more tapes. When I look at the tapes through at the Tape Infrastructure>Media pools. The tapes show the media set, expiration, capacity and free info. The Free column displays 4.9 out of 372.5 free. However when I go to browse the tapes I do not see anything. And Veeam continually asks for additional tapes as if it cant see data on the tapes either. I am using Veeam 126.96.36.1994. It is installed on a Dell R320 running Windows server 2012 R2. The tape drive is a Dell 124T. The tapes are LTO3. In the beginning when this first happened erasing the tapes seemed to do the trick. The second time this happened erasing the tapes did not help. But rebooting the Dell R320 and Dell 124T this time did. The third time this happened we upgraded the firmware on the Dell 124T, updated Veeam to the most recent patch and rebooted both the Dell server and auotloader. This worked. Now we are on our fourth time with this happening and none of the aforementioned steps seem to make any impact now.
I have searched Dell and Veeam forums and cannot find anything similar to my case.