ethernet and switches, was Re: [rescue] Mozilla Firefox

Dave McGuire mcguire at
Thu Apr 22 21:58:09 CDT 2004

On Apr 22, 2004, at 10:49 PM, Patrick Finnegan wrote:
>>> Anyways, unswitched FDDI, like unswitched ethernet, still doesn't
>>> scale well.
>>    Uhhhhh, where did you hear that?  Media utilization rates greater
>> than 95% are commonplace on FDDI.  It was built to scale, and it
>> does.
> Media utilization rate isn't everything.  If you've got 100 hosts a 
> ring, you've got a 1Mbit/sec average bandwith.  When you've got a
> cluster of 48 processors trying to chat with each other to run a
> multi-way job, that isn't good enough.  (This is for $work, not $home).
> If you hooked it up to a DEC GigaSwitch, then it'd be pretty nice.
> I'm *not* saying FDDI isn't useful for real work, just not at where I
> work.

   Ahhhh, the way you worded that suggested you felt it wasn't useful 
for *any* work.  I understand what you meant now.

   Quite simply, if you need more than 100Mbps of bandwidth, FDDI is the 
wrong tool for the job.

>>    Can I get an InfiniBand switch for the same twenty bucks that
>> bought me a Myrinet switch last fall? ;)
> Again, $work, not $home.  I picked up a Myrinet switch for $2 (one that
> uses the older, DC37 connectors) about a year ago.  It's nothing to
> sneeze at (>1GBit/s), but their current products leave a lot to be
> desired, compared to what other people offer.

   Ahh, I paid ten times what you did, sigh. :-|

> Ahh yes, and there's that scaling issue they seem to have with the
> number 128.  If anoyone around here has to deploy more than 128
> machines connected via Myrinet, watch out.  128 is the maximum number
> of nodes you can have on a Myrinet switch, and when you start to stress
> the connections between switches, the tend to break.  Myrinet is
> supposedly having trouble setting up their gear on a 1024 node cluster
> at NCSA because of this issue, and they've been working on it for a
> while.


> Of course, none of this really applies to the "rescue" part of this 
> what
> this list is about, at least for another couple of years.  Even I don't
> have >128 machines at home, let alone that many machines running, or
> which could use Myrinet cards.

   Do you have any of the cables?  Or do you know the pinouts & 
particulars of them?

> However, their older products are pretty nice, and they did have the
> market cornered on high-performance interconnects for a while.  If I
> had more than one adapter for my switch, I'd be using it, as it's the
> fastest networking gear I've got. Not bad for what is (IIRC) 5+ year
> old networking hardware.  Really Not Bad.

   I have a bunch of Myrinet interfaces...PCI and sbus.  I haven't done 
anything with them, for lack of cables.

>>> <set mode=$home>
>>> FDDI (and it's slower friend, Token Ring) are fun, but not useful
>>> for $work_stuff.
>>    Wrong.  Sorry, but dead wrong.
> You've gotta remember what I do for $work.  High Performance Computing.
> FDDI (unswitched) isn't.  Switched fast ethernet isn't.  GbE is getting
> there, and IB is pretty much there (for now).  We need something that's
> capable to do full-speed any-to-any communications for groups of 16-48
> machines.  If FDDI was switched, and did Gbit speeds, then it would be
> useful.  Same thing with TR.
> $home, $fun is much different.  FDDI/TR is useful and can do Real Work,
> they're just not useful for My Job. :)

   See above...I thought you meant *any work*, not your place of 


Dave McGuire          "PC users only know two 'solutions'...
Cape Coral, FL          reboot and upgrade."    -Jonathan Patschke

More information about the rescue mailing list