SOLVED: Simple swap question
jerrymc at msu.edu
Tue Dec 30 20:29:46 UTC 2008
On Fri, Dec 19, 2008 at 01:04:26PM -0500, FreeBSD wrote:
> Tom Worster a écrit :
> >On 12/19/08 10:37 AM, "FreeBSD" <freebsd at optiksecurite.com> wrote:
> >>Because this server is monitored by Nagios and it emails me every hour a
> >>warning because the swap is not 100% free (I know it's pretty extreme,
> >>but I want to know if the system is swapping).
> >if a swap space is available and swapping not turned off, it seems
> >reasonable to expect the OS to use it as it sees fit.
> >rather than trying to tinker with the kernel's swapping policy on the fly
> >every time you get a warning, perhaps think about either telling nagios not
> >to worry about it or don't use swapping. i'd go with the former. but you
> >you want to ensure that swap doesn't get used -- so maybe get rid of the
> >swap slice?
> This server is very lightly used, so most of the time if the swap is
> getting used it shows that something is going wrong.
This simply is not true. It may once have correlated with some
problem, but the fact that swap is used does not indicate any problem.
It indicates that the system is working properly.
> This warning
> already proved usefull once, so I don't think I'm going to change it. I
> don't want to mess with the kernel actions, but there was no reason to
> keep this in swap. I understand that the kernel can't know that, that's
> why I wanted to know the way to "reset" the swap. There is always a lot
> of free or inactive RAM and, in normal condition, the swap should not be
> used. It's been like that for months, so I think it's a good idea to be
> notified if the swap is used.
Really, before you go making that choice, you should study the ins and
outs of how swap is used. You will find that some amount of use, even
in a lightly used server, is desirable under almost all circumstances.
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