Hi,
I just ran some bonnie++ tests to measure the nfs performance of udp vs.
tcp, expecting tcp to be better (after reading this list and some newsgroups).
Amazingly, it turned out that udp with rsize/wsize 16k was the best, taking
the average over all tests. tcp was a little better in some of the large-file
tests, but especially with creating/stating/deleting 16 thousands of small
file, sequentially and randomly, udp was better than tcp in every test
(between 5-15 % faster). I rann all the tests also with differenct tcp windows
sizes, and a larger window size speeded up udp and tcp more or less in the
same way.
I was very amazed by this, but I guess this could be caused by our network,
which is a fully switched "100mbit for client/1gbit for servers" network,
so we have almost no packet loss.
If I got the discussions on the list and in the newsgroups right, on a
lossy network udp would slow down due to the packet loss and resends.
So, can my result be correct for a really fast and stable network? Or is
it some "bonnie++ likes udp" effect? :-)
cu,
Frank
--
Dipl.-Inform. Frank Steiner Web: http://www.bio.ifi.lmu.de/~steiner/
Lehrstuhl f. Bioinformatik Mail: http://www.bio.ifi.lmu.de/~steiner/m/
LMU, Amalienstr. 17 Phone: +49 89 2180-4049
80333 Muenchen, Germany Fax: +49 89 2180-99-4049
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I forgot to say: This is kernel 2.6.8.1 on server and client.
--
Dipl.-Inform. Frank Steiner Web: http://www.bio.ifi.lmu.de/~steiner/
Lehrstuhl f. Bioinformatik Mail: http://www.bio.ifi.lmu.de/~steiner/m/
LMU, Amalienstr. 17 Phone: +49 89 2180-4049
80333 Muenchen, Germany Fax: +49 89 2180-99-4049
* Rekursion kann man erst verstehen, wenn man Rekursion verstanden hat. *
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On Mon, Aug 23, 2004 at 11:57:40AM +0200, Frank Steiner wrote:
> Hi,
>
> I just ran some bonnie++ tests to measure the nfs performance of udp vs.
> tcp, expecting tcp to be better (after reading this list and some
> newsgroups).
> Amazingly, it turned out that udp with rsize/wsize 16k was the best, taking
> the average over all tests. tcp was a little better in some of the
> large-file
> tests, but especially with creating/stating/deleting 16 thousands of small
> file, sequentially and randomly, udp was better than tcp in every test
> (between 5-15 % faster). I rann all the tests also with differenct tcp
> windows
> sizes, and a larger window size speeded up udp and tcp more or less in the
> same way.
With a metadata-heavy workload like this the [rw]size makes little
difference.
> I was very amazed by this, but I guess this could be caused by our network,
> which is a fully switched "100mbit for client/1gbit for servers" network,
> so we have almost no packet loss.
>
> If I got the discussions on the list and in the newsgroups right, on a
> lossy network udp would slow down due to the packet loss and resends.
>
> So, can my result be correct for a really fast and stable network? Or is
> it some "bonnie++ likes udp" effect? :-)
There's nothing unusual here. On a low-latency uncongested unlossy
network, it's not surprising that UDP is faster. As soon as any
of those factors goes away, TCP starts winning.
Greg.
--
Greg Banks, R&D Software Engineer, SGI Australian Software Group.
I don't speak for SGI.
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Greg Banks wrote:
> There's nothing unusual here. On a low-latency uncongested unlossy
> network, it's not surprising that UDP is faster. As soon as any
> of those factors goes away, TCP starts winning.
Ok, thanks! I just wasn't sure about that.
--
Dipl.-Inform. Frank Steiner Web: http://www.bio.ifi.lmu.de/~steiner/
Lehrstuhl f. Bioinformatik Mail: http://www.bio.ifi.lmu.de/~steiner/m/
LMU, Amalienstr. 17 Phone: +49 89 2180-4049
80333 Muenchen, Germany Fax: +49 89 2180-99-4049
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[email protected] wrote:
> On Mon, 23 Aug 2004, Frank Steiner wrote:
> I don't know why you are so suprised. TCP has somewhat more protocol
> overhead than UDP. So on a solid network it should be faster.
I guess that was just because I was blended by the "tcp should be faster"
quotes, where I didn't read carefully enough to get the full story...
My fault :-(
--
Dipl.-Inform. Frank Steiner Web: http://www.bio.ifi.lmu.de/~steiner/
Lehrstuhl f. Bioinformatik Mail: http://www.bio.ifi.lmu.de/~steiner/m/
LMU, Amalienstr. 17 Phone: +49 89 2180-4049
80333 Muenchen, Germany Fax: +49 89 2180-99-4049
* Rekursion kann man erst verstehen, wenn man Rekursion verstanden hat. *
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On Mon, 23 Aug 2004, Frank Steiner wrote:
> I was very amazed by this, but I guess this could be caused by our network,
> which is a fully switched "100mbit for client/1gbit for servers" network,
> so we have almost no packet loss.
I don't know why you are so suprised. TCP has somewhat more protocol
overhead than UDP. So on a solid network it should be faster.
You can use larger packets with TCP than you can with UDP which can offset
the overhead some.
Ian
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