Showing results for 
Search instead for 
Did you mean: 

Maximum concurrent write drives set to 8 but only uses 5.

Level 4

We have 9 LTO-7 drives, maximum concurrent write drives is set to 8. We've also set the SLP Multiplexing to 8.


But jobs NEVER use more than 5 drives. Which used to be our old limit.


We bought 3 more drives, so I would expect it to use 8 like we configured the polices/lifecycles too.


Am I missing something?


I've verified the policies, the SLP.


Partner    VIP    Accredited Certified


so some of jobs are Queued, instead of Active, yes? In their details, you wil find a reason for queueing, so which parameter reached its limit. Maybe you have limits somewhere else.

You confuse multiplexing with multistreaming. When you increase multiplexing, you won't utilize more drives, you will just allow more streams to be running against one drive.



Level 6
Partner    VIP    Accredited Certified


You mention SLP Multiplexing

Are you referring to SLP Tape Resource Multiplier? 

Explanation from NBU Admin Guide: 

Limits the number of concurrently active duplication jobs that can access a single tape media storage unit to xx times the number of available drives. Allows tuning to avoid overloading the Resource Broker, yet makes sure that the devices are not idle. No minimum multiplier or maximum multiplier. Default: 2 (multiply access to the write drives by two).

Configuration entry default: SLP.TAPE_RESOURCE_MULTIPLIER = 2

So, depending on the amount of SLP jobs, there are probably not enough jobs for the amount of drives.
What happens if you return the tape resource multiplier to the default of 2?

No, It starts howevery many jobs I till it to, my issue is I have 9x LTO-7 Drives (we had 6 and bought 3 more). Originally our backups would use 5 drives leaving 1 for restores.


Moving to 9 drive setup, I'd like it to use 8 and leave 1 for restores, we adjusted The settings to have it use more drives, and relaunched the backup. But it only uses 5 drives still. Leaving 4 sitting idly.

Moving it back to 2, it still only used 5 of 9 possible LTO drives. This is what I am trying to acheive it to use more than the seeming limit of 5 we have.


I replied to another person on this thread with a little more information.

Did you update the properties of the Storage Unit to tell it the new amount of drives?

Listed under Storage -> Storage Units


Partner    VIP    Accredited Certified


how many backup jobs you run concurrently? Your multiplexing is set very high - with these parameters you need at least 80+ concurrent backup jobs to utilize 6+ drives (supposing target volume pool and retention are the same). The higher is mpx, the lower number of drives you need.

Dont use such a high value unless you have extremely slow clients. I use multiplexing set to 5 max. (for LTO6 and higher drives.)