Hi all,
I have searched the forums this morning around multistreaming and multiplexing (MDS and MPX) and I was surprised not to find anything about the media multiplexing level parameter controlled by policy and schedule.
Media Multiplexing definition:
"This parameter will control how many jobs/streams the class can multiplex on one drive". Source
http://support.veritas.com/docs/294159
The class being here the logical group configured through the policy and schedule.
Media Multiplexing behaviour:
Level 1 (danger!): set the level to 1 and it will result in an
EXCLUSIVE behaviour from your backup job, as it requires a tape drive to itself. Tested behaviour will see the job being queued until a tape drive is not in use or job will be active with no other jobs multiplexed onto the tape drive.
Obvious consequences: backup window explosion, poor infrastructure utilization and performances, drive shoe-shining...
Level x ≥ 2 (ok!): set the level at 2 or higher (drive multiplexing limit) and the backup job will happily join in the other active jobs onto the same tape drive. I need to do more testing to see how well the level is respected.
Conclusion:
Media Multiplexing level 1 really should be corrected to 0, as it enforces an EXCLUSIVE behaviour: one UNIQUE backup job at the time onto one Tape Drive.
I will update the thread with the results of additional tests, but feel free to confirm that you got the same results, as I am a bug collector. ;)
Kind regards,
Alex Rappoport