Niclas Sodergard writes:
> On 6/8/07, Roch - PAE <Roch.Bourbonnais at sun.com> wrote:
>
> > > from the V20z to the V240 gives me a write speed of 80MB/s. So my
> > > problem is that I get reading speed of 40MB/s over NFS and with the
> > > same options I get writing speed of 80MB/s. I'm having a really hard
> > > time to understand this and I was hoping someone here could provide
> > > some light in this very dark tunnel.
> > >
> > > What could cause read speed to be so much slower than write?
> > >
> >
> > This does not look extraordinary to me although, clearly it
> > could be bettern.
> >
> > To write, you're pushing data out, presumably at the speed of
> > the network with NFS responses (ack) coming in stride.
> >
> > To read, it's a request/response load. Send your request
> > wait for response. Because of the sequential streaming
> > access pattern, you should be hitting readahead codepath (in
> > the client client and server filesystem). That might not be
> > behaving optimally; so at times the network goes quiet while
> > a server side read is being braught in from disk.
>
> Thanks for your answer.
>
> I've continued to bash my head against the server and tried a few more
> options.
>
> 1. I removed the network switched and connected the machines directly
> with a cable. No changes.
>
> 2. I tried multiple reading streams but that doesn't change anything
>
> 3. I mounted the server to my linux workstation (running a 2.6.20
> kernel) and that machine is capable of reading 80MB/s. So clearly the
> V240+6140 is able to push the data.
>
> This makes me wonder that there must be something wrong/misconfigured
> with the Solaris 10 nfs client. I've tried googling a lot, checked
> sunsolve, google.groups but there doesn't seem to be any good answers.
> Are there any performance related parameters that I can change that
> could affect the nfs client?
>
The file is not fully cached right ? So to get 80MB/sec and
5ms I/O latency, you need 400KB of readahead window. I think
our clients manage 8 async threads per mount point (at 32K
per request you fall a bit short). You might try playing
with:
nfs3_max_threads
nfs4_max_threads
or use multiple streams from multiple mount points.
-r
> cheers,
> Nickus
>
> --
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> http://aspiringsysadmin.com
