Tugger the SLUGger!SLUG Mailing List Archives

Re: [Fwd: Re: [SLUG] IOWait definition]


On Fri, Oct 10, 2008, Adrian Chadd wrote:
> 

> Now, you could go groveling through the kernel to try and figure out
> whether IOWAIT includes "nfs activity" (which I believe would be
> the disk IO related to NFS, but it could be other things I guess) and
> first see if doing userspace disk IO does a lot of IOWAIT. Grab bonnie
> or some other hard disk throughput testing thing, run it, and see how
> much time is spent in IOWAIT. If you've got almost no IOWAIT time when
> doing it locally but IOWAIT time when doing it over NFS, you could be
> right. If you have IOWAIT time on both, I'd poke the disk/controller/
> driver combo. 
> 

I just re-re-read the OP and stuff and realise my assumptions don't match
your request. I assumed you wanted to know if IOWAIT included disk IO
time -and- nfs server time. But you're asking if IOWAIT include NFS
client time (ie, time spent on your box talking to the NFS server.)

Anyway, doing a bonnie++ or such test will still tell you. Run it locally
and run it over NFS. See if you get IOWAIT increases for both. That
should give you some hint as to whats going on. I've never seen IOWAIT
for NFS client traffic (ie, traffic from an NFS client talking to an NFS
server) but who knows, this is linux..



adrian

> 2d,
> 
> 
> 
> Adrian
> 
> 
> On Thu, Oct 09, 2008, David Kempe wrote:
> > Grant Street wrote:
> > >
> > >
> > >I have a machine with a good proportion of IOWait 20-30%. It does have
> > >local disks and it performs operations on NFS mounts. I just wanted to
> > >be sure if IOWait includes NFS activity or not. I also want a way if it
> > >is NFS to be able to say for sure if it is a bottleneck on the nfs 
> > >client or server. NFS is not a linux machine so visibility is not 
> > >allways the best.
> > >
> > dstat might help you correlate stuff.
> > http://dag.wieers.com/home-made/dstat/
> > 
> > dave
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