Swap space on SAN

[Don Spare]

I need to add some swap space but the only disks I have with sufficient space are on the Clariion SAN. Is this an acceptable place to put swap? I'm sure I can set up the appropriate LVM structures and then assign the extra swap space to them but is this a reasonable solution? Should I be working with 'internal' drives instead? I have been searching the forum for info on this but haven't seen anything yet on putting swap on SAN drives.

Thanks,

Don

[Pete Randall · Accepted solution]

Don,

I don't see why not. Their might be performance implications but if you're swapping, you've got performance problems already.


Pete

[Victor BERRIDGE]

Hi Don,
I do without any problem, you do have dual paths (alternates...) with 2 controllers/HBA dont you?

All the best
Victor

[Victor BERRIDGE]

I would add same size as the other swap space so that you have equitable load if swapping occurs


All the best
Victor

[Jeff Schussele]

Hi Don,

Absolutely it's OK.
And frankly IF you get to the point of actually paging out, where the swap is located won't mean diddly because performance will be in the crapper anyway. So put the space wherever you wish -- just don't ever page out to it - HAVE SUFFICIENT MEMORY.
You just generally need sufficient swap space to cover all the reservations that you'll need for the all the apps you'll be running.
Settinf swapmem_on=1 in the kernel will also enable pseudo-swap to help in the reservation effort IF you just can't provide all the "actual" swap space you might need.

Rgds,
Jeff

[Geoff Wild]

I do for some QA and DEV servers = as they are HW partitioned 7410's - so they only have access to 2 internal disks.

I have a 4GB primary swap on those internal, but secondary is on EMC...

The downside - if you need to do some major SAN work - then you have to shut down the servers - as HP-UX still doesn't have a swap off command .

Other than that - swap on SAN works great.

Rgds...Geoff

[Don Spare]

I forgot to tell you that my server is L2000 4GB RAM running HP-UX 11.0. Swap is currently set to 2GB. This server is primarily data warehouse (Oracle) with some small ancillary/tool/monitor programs too. I began this investigation because the Patrol agent detected the swap utilization to be around 92-94% three nights in a row during our peak DW loading time. The alert wasn't critical but that seems to be getting pretty close for me. BTW maxswapchunks = 3000 and swchunk = 2048.

Don

[Victor BERRIDGE]

So create a new 2GB swapspace on your SAN, if you dont have a dynamic load balancer then create 2 swaps of same size on 2 different vg if you have split the IO using alternate pathing.
On some systems on SAN where I had no dynamic load balancer I even went and create swap space on stripped LVM...

All the best
Victor

[Steven E. Protter]

If you must swap on the san:

Set the priority number higher than your local swap. This will make the actual priority lower therefore limiting the performance impact to only your peak processing time.

Also: consider more memory. It will help you get the work done faster.

SEP

[Rita C Workman]

I use my Symmetrix disk when I have a need for some SWAP. So some spare Clariion looks just as good - no better, cause it's cheaper..

Rgrds,
Rita

[Ted Buis]

As you know, Clariion would not be supported for any purpose by HP, and obviously not that you care. You still want to avoid page-outs, and if possible to slower devices. FC SANs typically have greater latency even if the arrays have good throughput.