[CentOS] athlon64/opteron 8GB per CPU

Mon Apr 10 19:28:58 UTC 2006
David Thompson <thomas at cs.wisc.edu>

I'm putting together a spec for a big(ger) memory x86_64 host, and I hope some 
of you-all can help.  I'm looking for success stories of hardware that folks 
are using in production environments, preferably with CentOS 4, with more than 
4GB of memory per CPU.

I know there are lots of mobos out there that can do this, but I'm looking for 
what folks really have running.  Call me paranoid.

The target is SATA + n*GigE + 1CPU + 8GB memory, and I can consider other 
configurations.  The incumbent system is a Xeon 8GB system running i686 CentOS 
4.3 (what else?), with light CPU loading and very heavy IO loading (WD raptors 
are our friends).

Folks with deep(er) knowledge of x86_64 architecture, I'd also be interested 
in the trade offs between 1CPU w/8GB and 2CPUs each with 4GB.  (E.g. what's 
the real cost of shipping data back and forth between the memory spaces of the 
two CPUs?  How does the 2.6 kernel deal with the split memory space?  etc...)  
The memory is all going to be used up in kernel buffers keeping bits of files 
in kernel memory.

Also, trade offs between Opteron and Xeon architectures, i686 vs. x86_64, 
bounce buffers, etc., for an application like this would be helpful.

The application is enhancement to a mirror server (mirror.cs.wisc.edu) here at 

Many thanks to all in advance.  Private or public replies welcome.

Dave Thompson