I have created a new media Set, with brand new tapes and this what I find:
Brand new tapes are being used. So there is no excuse for Condition of Tapes or Stopping and Starting of Backups.
I am using SAS connected locally to Active Storage RAID 6/mbps, so Source Speed is not applicable.
The capacity given is before any backup has completed. So No Compression issues are applicable.
Have not run a backup yet, so NO Media failures have occurred, so it cannot be a problem.
I understand its an estimate, but a 10TB loss is one hell of loose margin.
I've been using Retrospect successfully for many years and find it very good, but this is the first time using it with so much data. Maybe I'm doing something wrong?