topic Re: Extend Swap? in Operating System - HP-UX

Extend Swap?

joe_91 — Fri, 04 Aug 2006 11:26:46 GMT

This is my current swapinfo (having 15G). I need to increase to 22G.

# swapinfo -tam
Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 4096 0 4096 0% 0 - 1 /dev/vg00/lvol2
dev 8192 0 8192 0% 0 - 1 /dev/vg00/lvswap1
dev 3072 0 3072 0% 5242880 - 1 /dev/vg09/lvswap2
reserve - 15360 -15360
memory 19513 4242 15271 22%
total 34873 19602 15271 56% - 0 -
Can i increase the current lvol for swap? or should i create a new lvol like lvswap3 on vg09?

Thanks

Joe

Re: Extend Swap?

Patrick Wallek — Fri, 04 Aug 2006 11:31:54 GMT

I would just add a new swap LV.

My biggest question is why do you think you need to add 7GB more swap space? Your allocation looks fine. You don't appear to be paging out. Why waste 7GB of disk space?

Re: Extend Swap?

joe_91 — Fri, 04 Aug 2006 11:33:44 GMT

you are right. the SAP team says it is their standard to have around 20 G swap space.

Thanks

Joe

Re: Extend Swap?

A. Clay Stephenson — Fri, 04 Aug 2006 11:34:00 GMT

One of the requirements of a swap LVOL is that it be contiguously allocated so it's doubtful that the LVOL could be extended. In any event, a reboot would be required before the larger LVOL would be utilized. It's easier (and at least as valid) to simply allocate another swap LVOL. I assume you have set maxswapchunks large enough for the increased swap; if not, you will need to build a new kernel and reboot.

According to this swapinfo output, you aren't using swap so what makes you think that you need more swap space?

Re: Extend Swap?

DCE — Fri, 04 Aug 2006 11:38:34 GMT

Just make a new lvol.

Is there a specific reason you need that much swap? Your system performance would die before before you ever actually reached 15 GB of swap used.

You do need to have at least one for one swap for memory. psuedo-swap is a help in the area as well, if you have it enabled in the kernel. (swapmem_on=1)

Re: Extend Swap?

Patrick Wallek — Fri, 04 Aug 2006 11:43:53 GMT

Well, my first question to the SAP team would be -- WHY? Why do you think you need that much swap?

I mean, after all, that is what you bought all that RAM for.

Re: Extend Swap?

A. Clay Stephenson — Fri, 04 Aug 2006 11:44:01 GMT

The last time I was involved in an SAP install, the SAP installation routine actually looked for the amount of swap and would terminate if 3X memory weren't found; after installation, SAP would be perfectly happy with much less swap (and indeed the swap was never used). One solution is to add that terrible, awful filesystem swap at priority 8 or so; that make's the SAP install happy and you can later remove it.

If you are running more swap space than memory, running pseudoswap (swapmem_on=1) is pointless.

Re: Extend Swap?

joe_91 — Fri, 04 Aug 2006 11:54:15 GMT

Clay,

how would that priority be assigned?

thanks

joe

Re: Extend Swap?

A. Clay Stephenson — Fri, 04 Aug 2006 11:57:45 GMT

At boot time, priority is set by reading /etc/fstab; just look at your current /etc/fstab and it should be obvious. Man fstab for details. At run time the swap is specified with the -p option. Man 1m swapon for those details.

Re: Extend Swap?

sathish kannan — Sat, 05 Aug 2006 05:23:29 GMT

hi joe,

I don't know where you are going to create the new SWAP lvol, I mean which disk. If you are trying to create on a external SAN array, try to spend it to multiple spindles as much you can.

my 2 cents

Regards
Sathish