Swap Priority Question - Very Confused

[Roland Rebstock_1]

all, i have a N-Class system with 2 swap partitions, the swap priority at 0 and 1 on according to swapinfo. I need to have both of those swap partitions the same priority but when reviewing the /etc/fstab it shows both are set to 0 and sam does the same

swapinfo output
PRI NAME
1 /dev/vg00/lvol2
0 /dev/vg00/swap
/etc/fstab
/dev/vg00/lvol2 . swap pri=0 0 0
/dev/vg00/swap ... swap pri=0 0 0
See attached samswap for bmp of sam

Yet on another N-Class which also has 2 swap partions swapinfo shows them at both Priority 1 but the /etc/fstab shows
/dev/vg00/lvol2 . swap pri=0 0 0
/dev/vg00/swap . swap pri=1 0 0
swapinfo
PRI NAME
1 /dev/vg00/lvol2
1 /dev/vg00/swap
see attached 2ndsamswap

IM ALL CONFUSED

[Geoff Wild]

Interesting - my primary swap isn't even in my /etc/fstab - maybe that's your issue?


Rgds...Geoff

[A. Clay Stephenson]

Actually, if these two swap partitions are on the same physical volume, you want them to have different priorities because when interleaving swap on the same PV the head will be moving like a madman. Now having said that, it really doesn't matter because when you begin to swap the performance is going to be so bad that "you are rearranging the deck chairs on the Titanic".

[Roland Rebstock_1]

All, I have no choice at this time but to keep the priorities the same, Im limited right now since our last software upgrade and when the 1st system listed above hits 95% on the primary swap partition things start to die like shareplex, oracle psoft. I need it to be configured like the last machine.

[Sanjay_6]

Hi,

I do not think an entry exist for the primary swap "/dev/vg00/lvol2" in /etc/fstab. It was probably manually added.

Swap priority for the default swap lvol2 is always 1. any additional swap could be added at the same priority "1" or at "0". setting the additional swap to "0" helps is taking the load off the primary swap.

Also take a look at this doc.

http://www6.itrc.hp.com/service/cki/docDisplay.do?docLocale=en_US&docId=200000075322187

The itrc doc id is KBAN00000218.

Hope this helps.

Regds

[A. Clay Stephenson]

Well, in that case, if you think that adjusting the swap priority is going to fix you then prepare to be disappointed.

[Steven E. Protter]

There is a bug in HP-UX which I pointed out to support a few years ago. Sometimes even when you properly adjust priority on swap areas in 11i v1 they don't display correctly on the swapinfo command.

When I asked them when they planned to fix it, they said they had no plans to fix it.

I don't know whether it was a swapinfo bug or a bug with the way the OS actually swaps. My machines rarely actually use swap anyway.

This can increase confusion, so I thought you should be aware of it.

SEP