Hi Andreas!

On Di, 2009-05-12 at 16:15 +0100, Andreas Roussos wrote:
> Can you show us the contents of /etc/exports on your head node?
(rw,sync,no_root_squash)

> I've had a similar problem in the past and managed to get better
> write speeds by adding 'async' to my exports options (have a look
> at `man exports`).

Strange, I read http://nfs.sourceforge.net/ and in B6 they stated

"For the Linux implementation of NFS Version 3, using the "async" export
option to allow faster writes is no longer necessary. NFS Version 3
explicitly allows a server to reply before writing data to disk, under
controlled circumstances."

>>but<< in fact it gives me 100MB/s if I set the async option

> Hope this helps!
yes of course, I still don't understand if nfs3 in async mode 
with a 2.6 kernel is something dangerous. But now I know where
the bottlenec is. I will also try the no_wdelay option

thanks and regards

sven



> 
> Regards,
> Andreas Roussos
> Systems Administrator
> Operating Systems Group
> University College London
> 
> Sven Sternberger wrote:
> > Hello!
> > 
> > I'm looking for a way to improve our nfs performance.
> > We recently updated a small cluster (16 nodes). The nodes
> > mount a share via nfs.
> > 
> > I use nfs3 over tcp. I checked the disk write speed on the server
> > (450mb/s) and the network thruput (980 mb/s). I tried udp, the deadline
> > scheduler and large tcp buffers.
> > 
> > SElinux and auditd is disabled, the server (Dell2950 w 8GB memory,PERC5)
> > and my testnodes (Dell 1950 w 8 GB memory) both run 64bit SL5.
> > 
> > What I see is >> always << ~20MB/s writing speed (reading is
> > about 90mb which looks ok). I can see the 20MB/s also in
> > iostat.
> > 
> > Device:         rrqm/s   wrqm/s   r/s   w/s    rkB/s    wkB/s avgrq-sz
> > avgqu-sz   await  svctm  %util
> > sdb               0.00  6511.63  0.00 83.39     0.00 25892.36   621.00
> > 143.20 1552.83  11.96  99.70
> > 
> > My write test is:
> > time dd if=/dev/zero of=./testme bs=1024k count=1000
> > 
> > I would expect that the write speed is higher. So any advice or
> > explanation would be helpful
> > 
> > best regards!
> > 
> > sven