From: Brad Barnett <lists@L8R.net>
Subject: Re: knfsd brought to its knees, by a simple rsync or cp
 operation
Date: Tue, 1 Mar 2005 06:57:03 -0500
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On Tue, 1 Mar 2005 10:55:48 +0100
Olaf Kirch <okir@suse.de> wrote:

> On Mon, Feb 28, 2005 at 11:20:18AM -0500, Brad Barnett wrote:
> > I start a long and extensive cp -a process on the nfs server.  Local
> > 'ls' responses are instant.  Write and read operations are instant
> > (it's a raid 10) on the local box, as well.  However, my single remote
> > client's "ls" operation changes to a jerky, slow operation.. with
> > upwards of 5 second pauses in reads.
> 
> Are you using NFS over UDP? If you ping the server from the client, do
> the round trip time and packet loss rate change when you start the
> heavy IO jobs on the server?

I just tried, and ping times do not visibly change (0.1ms before and
after).

However, this is what is really erking me.  This isn't a heavy I/O job. 
This is just _one_ cp.  Nothing else is happening on the entire server!  I
just did, in the above test:

client: ls -R /home

The client is fine, for very long periods of time...

Then, while the above command is still happening:

server: cp -a /raid/home /raid/hometest

Within 10 seconds, the output of ls -R /home slows.  Within 20 seconds, it
_stop_.  It then sits there for seconds, and spews out a page in small
jumps.  Again, a ls /raid/home on the _server_ barely slows, and is
constant.

I'm really scratching my head here.


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