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From: liam@dcs.qmw.ac.uk (William Roberts;)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: seeking experiences with FDDI interfaces for Sun's
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Date: 21 Jun 91 10:05:25 GMT
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In <3384@redstar.dcs.qmw.ac.uk> liam@dcs.qmw.ac.uk (William Roberts;) writes:

>In <9106041306.AA09116@msr.EPM.ORNL.GOV> dunigan@MSR.EPM.ORNL.GOV (Tom 
Dunigan 
>576-2522) writes:

>3) It gives *no measurable performance increase* for NFS - even with both 
>client and server on FDDI and tests which don't involve server disk access 
>there is no increase in performance over Ethernet connections.

I had some mail saying:

|    I'd  be *fascinated* to read or hear more about your experiences
|with FDDI cards, especially Sun's and *especially* why Sun's doesn't
|get any speed inprovements with FDDI vs. Ethernet!

I'm quite prepared to believe that Sun4 machines (I was using a Sun 4/280 and 
a Sun 4/160) can drive the FDDI network at greater than Ethernet bandwidth: 
one of the planned experiments was to change the FDDI driver software so that 
it generated continuous "idle traffic" transmitting strips of a VME 
framebuffer, sending to another machine which writes such things direct into 
its display memory.

What my experiments showed was that there is no performance improvement for 
NFS operations benchmarked with the Legato "nhfsstone" benchmark: I've a paper 
on this in the UK Sun User Group conference in September (in fact an extention 
of a paper I gave at the European Unix User Group Autumn '90 conference) and 
that's probably the best way to look at what I've done. There should be a 
report on the overall FDDI Pilot project (it's being done for the JNT: the 
body which runs the UK academic network) but I don't know the timescale on 
that any more.

FDDI doesn't make any difference because present machines can't really compute 
at those speeds (well, Crays and the like perhaps, but nothing that Sun 
manufacture). The only applications which ship data around that fast and which 
might benefit from FDDI are ones where the machines at either end don't have 
to manipulate the data as it comes in - they just pump bursts of data for 
later use. Obvious examples are live video and very low-level data transfer 
between peripherals (FDDI started life as something for IBM channels, I 
believe): the only one which seems pertinent to workstations is swapping over 
FDDI.
--

% William Roberts                 Internet:  liam@dcs.qmw.ac.uk
% Queen Mary & Westfield College  UUCP:      liam@qmw-dcs.UUCP
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