[CentOS] Centos 7.0 and mismatched swap file

Mon Feb 16 02:16:11 UTC 2015
Gregory P. Ennis <PoMec at PoMec.Net>

On Sun, 2015-02-15 at 17:37 -0800, Keith Keller wrote:
> On 2015-02-15, Gregory P. Ennis <PoMec at PoMec.Net> wrote:
> >
> > I am putting together a new mail server for our firm using a SuperMicro
> > with Centos 7.0.  When performed the install of the os, I put 16 gigs of
> > memory in the wrong slots on the mother board which caused the
> > SuperMicro to recognize 8 gigs instead of 16 gigs.  When I installed
> > Centos 7.0, this error made the swap file 8070 megs instead of what I
> > would have expected to be a over 16000 megs.
> 
> You lucked out, honestly.  You really don't want 8GB of swap on your
> system.  What will most likely happen is that you'll have a process that
> starts running away eating memory, and it'll try to use all of that swap
> before the kernel's OOM killer can kick in.  You will not enjoy
> thrashing 8GB of swap for probably hours.
> 
> Really what you should do is drastically reduce the amount of swap you
> have allocated, and reclaim most of that 8GB of swap space for storage
> filesystems.  In my experience, a few hundred MB of swap is more than
> sufficient to be able to swap out seldom-used memory while not taking
> too long to OOM.  If you really find a need for more swap later, you can
> allocate a swap file; it's slightly less efficient than a swap
> partition, but compared to real memory the difference will be
> negligible.
> 
> --keith
> 

I am sure glad I did not start over on the installation.  Thank you to
everyone for the information and education!!!!!

Thanks again!!!!

Greg