I have a tape library with four tape drives. Right now all of our backup jobs are single stream, and Networker chooses which tape drive to use by itself, with job parallelism allowing more than one job to write to a particular drive at a time.
Now we have Networker 9.x, I want one job in particular to use parallel save streams to improve throughput, but to only save to one tape drive (i.e. four streams to a single drive, rather than two streams to two drives). How do I do this without limiting the pool to a specific drive?
You should do that by increasing the Target Sessions for each tape drive.
But be careful about the consequences:
- If your max data rate is already achieved with a single stream, this would not improve your backup speed at all.
- Instead it would lead to the slower restore of a single streams because the drive must read 3/4 of data which is not needed by this save sset.
Always think about what is your most important goal to achieve:
- Do you want to optimize for a specific operation ... or ...
- Do you want a general solution which is a bit slower but work on most conditions pretty well.
Thanks, but my tape drives already have Target Sessions set at 4. Networker splits the four parallel save streams across two drives anyway.
May I suggest you contact EMC support. Maybe there is a hidden (debug) variable which you may set to disable save stream distribution.