how does Netbackup pick up available drives?

[FlyMountain]

When i try to balance the traffic for my 10 drives between two FC paths. I am confusing with following two options:

1. assign first 10 drives to one path with continous LUN numbers, and another 10 drives to seond path

2. assign 10 drives with even LUN numbers to one path, another 10 with odd LUN numbers to second path

Just want to make sure if multiple drives selected by Netbackup, two paths can be used evenly for traffic balance.

Not sure how Netbackup picks up the drives. But looks neither way can really balance the traffic, the drives to be picked up randomly. 

Can anybody help confirm it?

thanks,

[Mark_Solutions · Accepted solution]

Netbackup loadbalances drive and tape usage It will put the tape with the least number of mounts into the drive with the lowest mount time So you really have little chance of acheiving what you nee d without some very clever maths and even then it would be near impossible Hope this helps!

[FlyMountain]

Thanks Mark. it is great to know and explains what i see.

[Nicolai]

Automatic load balance does only work for disk disk drives using a balance software like PowerPath or VxVM.

For tape drives you do not have the same options. Netbackup tape drive allocation is based on a number of factors like, last usage count, media availability, Media server load, already mounted tapes etc etc. Trying to predict all factors will be a tough job.

Netbackup does allow multiple path to one tape drive for but that is for connectivity reason, not load balance.

Quote from NBU 7 Options:

Increased fault tolerance—Access additional tape resources in the event of a drive or network failure;

includes support for multiple paths to tape drives.

Personally I wouldn't place more than 2-3 tape drives on one FC HBA.