Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!newstop!west!iliad.West.Sun.COM!jstampfl
From: jstampfl@iliad.West.Sun.COM (John Stampfl - Sun Silicon Valley SE)
Newsgroups: comp.protocols.nfs
Subject: Re: how many nfsd's should I run?
Message-ID: <1466@west.West.Sun.COM>
Date: 28 Feb 91 17:04:10 GMT
References: <28975@cs.yale.edu> <4541@eastapps.East.Sun.COM>
Sender: news@west.West.Sun.COM
Organization: Sun Microsystems, Mt. View, Ca.
Lines: 52

>Q: So what are the magic formulas for a starting value?
>
>Variation 1-- #(disk controllers) + 1
>Variation 2-- #(disk controllers) + #(ethernet interfaces)
>Variation 3-- #(disk controllers) * min(4, #(spindles/controller))
>Variation 4-- 4 for a small server, 8 for a midsize server, 16 for a large server

Chuck,
	I have found serveral problems when there are not enough nfsd's in
particular, "server not responding", slow copies from a fast client to a
slow server.

Also, running with presto or presto and OMNI usually requires less nfsd's or
OMNI_nfsd's.

	I like 24 nfsd's as a starting value on all pure nfs servers, if you
are doing compute serving also, or comms or other cpu intensive job, you may
want a smaller number.

>>What happens when you run too many nfsd's?  
>Server performance may suffer.  
I haven't seen nfs server performance suffer, but have heard of mixed cpu/nfs
servers suffering.


>On machines with hardware support of multiple contexts (ex:
>Sun4/SPARC), running more nfsd's than there are hardware contexts will
>force context switching into software.

I believe that nfsd's run in kernel space and thus donot do hardware context
switches.
>
>Q: Why do some people run very large numbers of nfsd's, 48 or even 64?
>
>'nhfsstone' benchmark results can often be improved by running a very
>large number of nfsd's on the server under test.  Doing this proves
>that it's possible.  Doing this does not prove that it's helpful on a
>production server with a mixed or bursty workload.

I have not seen much improvement in running over 24 nfsd's.  The curve has
flattened out.  With omni and presto 16 may be enough.

One thing, If you have a system with nfs performance problems and running
less than 24 nfsd, try 8 or so more, you may also need to increase maxusers
In may experience going to 24 nfsd's or so doesn't hurt much, except for small
memory cpu/nfs servers.  If more nfsd's don't help, then the lack of nfsd's
wasn't the problem and you can reduce the number.




Keep up the good work, maybe someday I will understand what is going on.