topic Re: swap area in Operating System - HP-UX

swap area

Bawitdaba — Fri, 15 Nov 2002 15:44:07 GMT

is there a maximum limit in swap area to get available?
I know that the recommendation is equal to the physycal memory as minimum, and from two to four times with some applications.
But i don't know if i can increase maxswapchunks kernel parameters as much as i want
thanks

Re: swap area

Patrick Wallek — Fri, 15 Nov 2002 15:56:01 GMT

Check out this page for information on maxswapchunks.

http://docs.hp.com/hpux/onlinedocs/939/KCParms/KCparam.MaxSwapChunks.html

The maximum value is 16384. If you set it that high, then you could have a total of 32 TB (yes, TERAbytes) of swap space.

One thing to keep in mind though, with the cost of RAM nowadays, you should NEVER EVER actually need to write anything out to swap space. If you do, then you need to buy more RAM.

The recommendations of some vendors, who shall remain nameless, that you need multiple GB of swap space is ridiculous and is only costing you $$$$ for disk space.

Re: swap area

S.K. Chan — Fri, 15 Nov 2002 15:58:14 GMT

There is no limit to the amount of swap you can configure but nowadays the rules of swap having to be 4x the amount of memory no longer applies. This is because you can make use or enable of pseudo swap on a big memory system with less swap space. The maximum amount of swap is determione maxswapchunks (default is 256) and the swchunk parameter (default is 2048). The formula for the maximum swap space :-
maxswapchunks*swchunk*1024bytes
For example (taking the defaults..) :-
256 x 2048 x 1024 bytes = 512MB
Increase maxswapchunks accordingly to get a bigger swap space.

Re: swap area

Jean-Louis Phelix — Fri, 15 Nov 2002 15:59:54 GMT

Hi,

You can increase it, I always put it high (> 10000) to avoid kernel rebuild in case of unexpected swap demand.

Regards.