On Tue, Dec 11, 2012 at 4:01 PM, Steve Thompson <smt at vgersoft.com> wrote: > 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. Could you perhaps elaborate a bit on your scenario? In particular, how much memory and CPU cores do the servers have with the really high NFSD counts? Is there a rule of thumb for nfsd counts relative to the system specs? Or, like so many IO tuning situations, just a matter of "test and see"?