Physical Swap Space Configuration with Pseudo Swap on and Large RAM

[Trojan36]

We have a partition on a large superdome with large amount of RAM (256GB) configured and is using pseudo swap.

What’s HPs recommendation in terms of configuring physical swap in this configuration. Is it needed, or should they just continuously monitor Swap space usage.

thx in advance

[Dennis Handly]

What does "swapinfo -tam" show? What HP-UX version?
If you have lots of RAM you really don't need that much swap.
If you think you need to add device swap, you'll be suffering performance.

[Emil Velez]

Do you ever need swap ? Configure enough swap for a crash dump of the system. Not all pages of memory go into a crash.

crashconf -v

will give you a estimate of how much space a crash will take.

Maybe 20 GB might be enough..Depends if you ever get to the point where you might need real swap.

pseudo swap is not real swap. ITs just a way to allow programs to use all of physical memory without having to reserve real swap to start processes.

[Michael Steele_2]

http://forums11.itrc.hp.com/service/forums/questionanswer.do?threadId=1408308

http://forums11.itrc.hp.com/service/forums/questionanswer.do?threadId=1408361

[T. M. Louah]

You need to determine if your system is paging? depends on the application(s) running on your server, usually software vendors will tell you how much swap their application needs to run properly .. for HP-UX tuning and memory management you can start at:
http://docs.hp.com/en/1219/tuningwp.html

t#

[Dennis Handly]

>T. M. Louah: You need to determine if your system is paging?

This won't answer the initial question about how much device swap is needed, if you have more than enough RAM.

>depends on the application(s) running on your server

Right. If you are running out of swap or want to add more applications, you may need to add more.

[AVV]

Hi,

It is not necessary to configure swap memory if you have enough memory to work with. The only thing when you have to consider the swap is when you may require a core dump to analyze. So, it is always advisable to set the swap memory (may be to 30G) so that your system may dump on it.