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EVA5000 and Secure Path on HP-UX (performance and config)

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Florian Doerfler_1
Occasional Visitor

EVA5000 and Secure Path on HP-UX (performance and config)

Hello everybody,

I've got a question mainly regarding secure path on hp-ux. I talked to a HP technician the last days, and he said that one should create more smaller vdisks (and then use LVM) instead of one big. That would be better, because the traffic would not go through one device file.

Now I saw on an other installation (see attachment), that secure path was configured to use more device files per LUN and controller (thus having, i don't know, e.g. 32 paths per LUN).

Is this what the HP technician meant, just another approach (instead of more LUNs, more device files per FC controller)? But wouldn't I still have the bottleneck (if it really is one), since I sill have one disk device file per LUN visible?

Now I wanted to setup Secure Path that way, so I have multiple path instances per controller/LUN. Does anybody know how to do this? Or is all this nonsense and I should do it the standard way?

Thanks in advance for your help and time.

Best regards,
Uwe Zessin
Honored Contributor

Re: EVA5000 and Secure Path on HP-UX (performance and config)


as far as I understood, the 'problem' with HP-UX is that it has a rather short I/O queue (8) by default. That is fine if you have a lot of single physical disks, but becomes a problem with larger LUNs, because there are no longer enough outstanding I/Os 'in flight' to hit all disks (in a disk group) of an EVA or other storage array.

My quess is that creating additional paths for Secure Path (either by tying all controller ports to all adapters, which I would not do[1] or by putting more adapters to the controller ports) will not help, because HP-UX will apply the limit to the secure path device (c12t0d0 in your case). Even if you enable load balancing it will not help, because the OS is not feeding enough I/Os to 'c12t0d0' which could then be balanced over the paths.

If you want to create multiple virtual disks, be aware that the EVA has a limit of 512 VDs and I think this includes any snapshots. On the other hand I have read somewhere that it is possible to increase the number of outstanding I/Os on HP-UX.

[1] it would mean that you run the EVA in one fabric, so it is not longer in a 'high availability' configuration.