Re: NFS performances

[Jan Stary <hans%stare.cz@localhost>]

On May 12 14:17:33, jlmuir%imca-cat.org@localhost wrote:
> On 5/12/14, 10:03 AM, Emmanuel Dreyfus wrote:
> > Hello
> >
> > I have a NFS setup with both NetBSD 6 client and server over a gigabit
> > network. Theperformance seems week, even whle client, server and
> > network are almost idle.
> >
> > The test: time dd if=/dev/zero of=test bs=1024k count=100
> >
> > Done on the NFS server itself:
> >    5.31s real 0.00s user 0.39s system
> >
> > Done over NFS:
> >    9.82s real 0.00s user 0.12s system
> >
> > The overhead looks huge. This is a UDP mount with a 1500 bytes MTU,
> > ping is at 0.8 ms from a virtualized client, ang 0.28 ms for a
> > physical one.
> >
> > Are the numbers reasonable? Should I consider a 59% NFS overhead as
> > acceptable, or are there some parameters to tweak?
> 
> Hi, Emmanuel.
> 
> RHEL 5 machine writing to an NFS v3 mount over GigE (1500 MTU):
>    1.22s real 0.00s user 0.06s system
> 
> That's way faster than even your local test.  So, I'd say your numbers
> do not seem reasonable.

We don't have any kind of detail for this comparison to even make sense.
How exactly is the filesystem exported? How exactly is it mounted?
In particular, is it async on linux? Is it even the same server?

> Have you already determined that the problem is with NFS,
> not the network

What "problem"? I still don't get it: writing over a network
is considerably slower than _not_ writing over a network, sure.

> (e.g. by using netperf or maybe just "time dd if=/dev/zero
> bs=1024k count=100 | ssh NFS_SERVER 'cat > test'")?

Ech, this brings irelevant influences into your "measurement";
for example, how much of that time is spent by ssh encrypting
and compressing the data (which has nothing to do with
your network performance)?

        Jan