Mixing Tape and Disk on a single dual-port HBA

[GavinR]

I know it's bad practice to mix tape and disk on a single HBA, but is there any guidance on if it's OK to mix them on a dual-port HBA?

We have a QLOGIC QLA2342 HBA (dual-port) and want to drive our disk through the first port and our tape through the second port.

The ports are supposed to be independent, so I'm guessing it's fine, but can't find any confirmation.

 

[nezih]

it's dual port single hba... not independent...

 

[heada]

If the OS sees it as two adapters, then I'd say it was OK. If the OS sees it as 1 adapter, not OK. Unless you're going to be tweaking the port settings then all you're doing is keeping the traffic seperate so that you get the same type of data (streaming vs random) on the same adapter.

You'd have a single point of failure (single HBA) but your traffic would be seperate which is what the "one for disk, one for tape" best practice is all about.

-Aaron

 

[PJ]

I think the old recommendation not to mix disk and tape on the adapters originated from the cases in which the tape workload sort of stragled the smaller disk i/os off, leading to databases literally falling asleep and things like that - plus a certain inflexibility when it came to finetuning the adapters. We have gradually started mixing here and there and have had no problems with modern hardware - at least not under AIX. Anyway: The 2-Port adapters should be 2 separate entities which just happen to share a bus slot. I don't think the "don't mix" rules apply for that setup.

PJ