topic Re: Swap Space in Operating System - HP-UX

Swap Space

Mike Kuhar — Fri, 25 Apr 2003 11:00:34 GMT

I need to install a patch bundle. It requires more disk space on vg00 than what I have available. There is 2gig of disk allocated to primary swap in vg00. I have plenty of EMC disk space available.

Can I reduce the size of the 2 gig swap in vg00 by 1 gig, and put that 1 gig on an EMC drive? If I can, what would be the shortcomings?

Re: Swap Space

James R. Ferguson — Fri, 25 Apr 2003 11:19:10 GMT

Hi Mike:

Reducing the size of primary swap is possible but requires at least two reboots and the use of LVM maintenance mode. See Technical Knowledge Base doucment #KBRC00004288 for the details.

Regards!

...JRF...

Re: Swap Space

Jeff Schussele — Fri, 25 Apr 2003 11:44:27 GMT

Hi Mike,

Yes that's possible, but as pointed out it's a lot of work.
You may wish to consider the alternative - extend vg00 with a LUN from the EMC array.
This is easy IF the constraining LV(s) are /var, /usr or /opt AND you have OnLine JFS. But if it's / or /stand that's short you'd have to reorganize vg00 using an Ignite tape.

Rgds,
Jeff

Re: Swap Space

Mike Kuhar — Fri, 25 Apr 2003 12:22:35 GMT

I thought that might be a valid alternative. Thanks. I do that instead.

Re: Swap Space

James R. Ferguson — Fri, 25 Apr 2003 12:33:42 GMT

Hi (again) Mike:

The downside of 'vgextend'ing another disk into vg00, *unless* you don't care if you keep a multi-volume vg00, is that when done, you will need to reduce both the filesystem and the logical volume that you enlarged.

Then, unless you have Online JFS 3.3 the liklihood of a successful dynamic reduction of the filesystem is poor. In that case, in order to reduce the filesystem you will need to back it up; recreate it; and reload it. Most likely this will need to be done in single user mode.

Long range, you might consider purchasing a larger physical disk for vg00 and re-igniting (with 'make_tape_recovery' your system onto it to give you the space you need. If that isn't an option, perhaps the reduction in primary swap *is* worthwhile. Of course, add secondary swap space on another physical device to compensate.

Regards!

...JRF...

Re: Swap Space

John Poff — Fri, 25 Apr 2003 12:43:46 GMT

Hi Mike,

I just wanted to cast a tiebreaking vote here and side with JRF. It will be much easier to take a PV from your EMC and put it in some other VG [other than vg00] or even create a new VG and make a filesystem just for loading your patch bundle. Then, you can blow it away when you are done without messing with the rest of the system. The patch bundle should be happy loading from most any place as long as there is enough room for it to live.

The hardest thing to do would be to grab some space from swap. I would only consider that as a last resort.

JP

Re: Swap Space

Steven E. Protter — Fri, 25 Apr 2003 14:18:25 GMT

The problem I see overlooked so far is if vg00 is so full, you're not going to have room to isntall the patches.

What is really needed is an increase in allocation to vg00 on the EMC followed by an increase in the /var filesystem.

If you have online JFS you should be able to get through it without a boot if you're 11.11. Otherwise its single user mode to expand /var

I'd like to see a bdf or a bdf /var

SEP

Re: Swap Space

Tim Sanko — Fri, 25 Apr 2003 14:23:18 GMT

I have a small 256 M on vg00 and secondary swap on my symmetrix 8430. I repartioned vg00 with ignite,
and added secondary swap on
and when I moved /tmp to the symm I got a very surprising boost in performance.

/tmp on /dev/vgsymtmp/lvsymtmp

Regards

Tim

Re: Swap Space

Bill Hassell — Fri, 25 Apr 2003 16:04:50 GMT

2Gb of swap space is a lot for the primary swap space, so re-igniting (make_tape_recovery) is the best way to go. Putting additional swap space on other disks has no measureable effect as you should not be using swap space on a busy system. The exception might be for very slow, highly interactive applications where swapping occurs every few minutes.

Look also at the cleanup command to help with /var/adm/sw and perhaps consider moving that directory to another volume group. This directory can get VERY big and is very seldom used except when installing software and patches.