Kaushal Shriyan kaushalshriyan@gmail.com wrote:

I have loaded CentOS 5.6 on HP DL 180G6 2U Rack Server and the physical RAM is 32 GB. As per http://www.centos.org/docs/5/html/Deployment_Guide-en-US/ch-swapspace.html It says it should be 1 x of Physical RAM or less. Not sure about the "less" word in deciding swap space size

IIRC, the traditional rationale behind having at least as much swap space as physical memory has to do with being able to save a core file (on reboot) if the kernel bites it. Different UNIX variants had slightly different concerns and values (in some cases 2x physical memory).

Other things that can influence wanting a lot of swap are: - if you need to support hibernation - if you're using kexec (I think) - if you're using tmpfs filesystems to any degree - if you're using a serious amount of buffer cache (such as on a file server) In all of those cases, swap will generally be used in a sensible fashion; you may use a lot, but that doesn't imply thrashing.

Without those circumstances, you still want a reasonable amount, but I'd be less concerned with matching the amount of physical RAM. The rule of thumb I use to start on CentOS systems is a minimum of 2G total or 1G per core, whichever is greater. Despite that, if your swap in/out parameters are consistently non-zero, you're best to solve it with RAM.

If you put your swap on an LVM volume, you can always easily tune it up and down as your needs change.

Devin