[K12OSN] Freeing Server Memory

[Mike Heins]

Quoting DWatkins at frkl.wnyric.org (DWatkins at frkl.wnyric.org):
> I've got the Enterprise Linux (Centos) running on a Dell 1425SC with two 
> Xeon processor and 4 gigabytes of memory. I'm also serving DHCP for our 
> network and serving about 19 thin clients that are PXE booting to the 
> K12LTSP server. When I first started the server last month I was using 
> about 240 MB of RAM and today I noticed that was up to over 2 gigabytes of 
> RAM. I recently ran "up2date" and updated the kernel and all packages. I 
> am running the smp kernel.  How can I keep my memory free?  Any 
> suggestions?
>

My suggestion is not to worry about it. You will probably notice that
a lot of that memory is in buffers and cache; this is good. In fact,
you don't really want/need memory free. You want it working for you.

If you are talking about the quiescent condition prior to clients
logging in, then perhaps it might be nice to have the memory "free".
But memory in cache and buffers is just as good; that will be 
cannibalized as necessary.

You mention Centos, but without version we can't know the kernel
version. If it is a 2.6.x kernel, the Linux memory manager does an
outstanding job of maintaining virtual memory. When a system is 
running its normal workload, you actually want little memory free;
because the more that is used in buffers and cache the better your
application performance will be (presuming those applications read
disk).

If you have an older 2.4.x kernel, consider an upgrade. I have been
running Linux servers for 10 years. The virtual memory manager in 2.6.x
does a much better job than the prior kernels, and should allow your
system to handle its workload in the most efficient fashion. I run
2.6.x exclusively now for this reason.

-- 
Mike Heins
Perusion -- Expert Interchange Consulting    http://www.perusion.com/
phone +1.765.647.1295  tollfree 800-949-1889 <mike at perusion.com>

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