Re: NFS performances

["J. Lewis Muir" <jlmuir%imca-cat.org@localhost>]

On 5/12/14, 2:27 PM, Jan Stary wrote:
> 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.

Hi, Jan.

True, I was just trying to give something for comparison under the
assumption that something was better than nothing.

> How exactly is the filesystem exported?

With the following options:

  rw,no_subtree_check,sync

> How exactly is it mounted?

With the following options:

  retry=1,bg,intr,noatime,nodev,nosuid,timeo=20

> In particular, is it async on linux?

It is not async, and both the NFS client and server are on Linux.

> Is it even the same server?

I'm not sure what you mean.  Do you mean is the NFS server running
NetBSD 6 and the same NFS code as Emmanuel's?  No, the server is running
on Linux.  But I was just trying to give a ballpark comparison showing
that Emmanuel's setup wasn't even close, thus suggesting something
wasn't right about it.

>> 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)?

That's true.  Note that I suggested netperf first.  Still, the
dd-over-ssh thing was just a quick thing to try.  I wouldn't think
encrypting the data would be that hard on the machine, and if the
dd-over-ssh thing was grossly faster, it would suggest that something
was definitely wrong with the NFS setup.

Lewis