We have a lot of tapes LTO4 from a older Microsoft DPM installation that will be used in a new VBR installation.
After do the erase ( short or long ) the tape in the Free Pool show the correct capacity and free space ( 780GB ).
When a tape Job is started, in 450GB it request another tape because the first is full.
The LTO4 is a 800GB native capacity. I think that this capacity need to the reached ( 780GB after the format ).
We also did the Tape Erase with the vendor utility ( more than 03 hours to complete ) and the result is the same.