On 3/13/19 5:26 PM, William Muriithi wrote: > Hello, > > I have 4 dozen of tapes that have the same product number, are labelled 6.25 > TB capacity and hence should all be holding about 6 TB. However, I have > noticed no consistency in their capacity at all. Sometime, they fill up with > as little as 2 TB and oddly can sometime handle 9TB, which is above the tape > capacity. > > Why is there such inconsistency? Is it a configuration issue or is this > something that is expected with bacula backups?
There are two principal factors: 1. Varying levels of compression achieved on the data The marketed 6.25TB capacity assumes roughly a 2:1 compression ratio achieved. If you get no significant compression in a data set, or it is already maximally compressed, you'll only get about 3TB on the tape. If it compresses really well and you average 4:1 compression across the dataset, you may see as much as 12TB. 2. Tape errors If Bacula encounters unrecoverable block errors writing a tape, it will not attempt to write any further data to that tape, but will put an EOT mark before the failed block and mark the tape full, even if not at the physical end of tape. -- Phil Stracchino Babylon Communications ph...@caerllewys.net p...@co.ordinate.org Landline: +1.603.293.8485 Mobile: +1.603.998.6958 _______________________________________________ Bacula-users mailing list Bacula-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-users
