On Tue, Dec 11, 2012 at 4:01 PM, Steve Thompson <smt@xxxxxxxxxxxx> 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"?
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