[CentOS] home directory server performance issues

Tue Dec 11 22:01:11 UTC 2012
Steve Thompson <smt at vgersoft.com>

On Tue, 11 Dec 2012, Dan Young wrote:

> Just going to throw this out there. What is RPCNFSDCOUNT in
> /etc/sysconfig/nfs?

This is in fact a very interesting question. The default value of 
RPCNFSDCOUNT (8) is in my opinion way too low for many kinds of NFS 
servers. My own setup has 7 NFS servers ranging from small ones (7 TB disk 
served) to larger ones (25 TB served), and there are about 1000 client 
cores making use of this. After spending some time looking at NFS 
performance problems, I discovered that the number of nfsd's had to be 
much higher to prevent stalls. On the largest servers I now use 256-320 
nfsd's, and 64 nfsd's on the very smallest ones. Along with suitable 
adjustment of vm.dirty_ratio and vm.dirty_background_ratio, this makes a 
huge difference.