How can I prioritise Duplications to tape over Duplications to disk?

[CadenL]

I have a NetBackup 8 media server with an MSDP and locally attached tape library.

This media server does not backup any clients directly but recieves duplication images into it's MSDP from another media server. It then duplicates these images to tape before expiring the image on it's MSDP. All this is controlled within an SLP

The MSDP is configured for 16 streams and I'm finding that all 16 streams are taken up by duplication images from the other media server and so the tape duplications just sit in a queue. I want to prioritise the tape jobs so it doesn't queue but will instead take the next available stream as soon as one becomes free.

The source MSDP for the disk duplication images has 32 streams as it handles a lot of client backups as well as the duplications to the tape media server. I don't want to reduce the number of streams here unless I can do it in a way as to not impact the backup jobs.

I know I can limit the bandwidth used by duplication jobs using the agent.cfg file - is there also a setting to limit the number of duplication jobs that can be active from a defined source?

thanks in advance

[Marianne]

When you say 'The MSDP is configured for 16 streams', is this the Storage Unit setting 'Maximum Concurrent Jobs Count'? 
And perhaps 'Maximum I/O Streams' setting on the disk pool set to the same value?

This is how these values are different:
STU setting limits the amount of concurrent writes.
Disk pool setting limits the total amount of I/O streams (read and write). 

So, if you increase the disk pool setting to 32, then 16 streams can write and 16 duplication jobs can read.

You just need to ensure that the underlying hardware can accommodate this amount of I/O. 

As far as Job Priorities are concerned, there is only an option for Duplication. 
There is no option to prioritize the storage type.

[CadenL]

Ah! - Brilliant

It's the storage unit that's set to 16 streams - but I suspect the Disk Pool is also set to 16 streams too. So in theory - If I increase the Disk Pool streams by 4 (to a value od 20) this will mean that 16 streams will be able to write to the pool (these will be my 16 duplication jobs from the source MSDP) AND there will then be 4 more streams that will only be able to read from the pool and these should get picked up  by the duplication to tapes job and would allow for all my 4 tape drives to be active at the same time.

That's extactly what I'd be after.

That way I wouldn't need to worry about prioritising the tape duplications as there will always be a 'read only' stream available they can use and so they wouldn't need to contend for one of the 16 read\write streams

[CadenL]

Sorry to bring this back to the forum.

It turns out the the 'Limit IO' feature wasn't enabled on the Disk Pool and therefore unfortunately not the fix for the issue. Is there anything else it might be?

We seem to still be in the situation that the deuplication to tape jobs don't run if all 16 streams to the MSDP are active. At least this is the behaviour we are seeing. I just want to double check there aren't any other potential config files that can prevent reads from the MSDP other than the disk pool 'Limit IO' settings before I log a call with support.

The max number of jobs per client is set to 10 (but I don't think this is a factor). Would there be any settings on the SLP config files? 

kind regars