Kaushal Shriyan <kaushalshriyan@xxxxxxxxx> 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
--
If you have any trouble sounding condescending, consult a UNIX user.
_______________________________________________
CentOS mailing list
CentOS@xxxxxxxxxx
http://lists.centos.org/mailman/listinfo/centos
