[Beowulf] building Infiniband 4x cluster questions

Vincent Diepeveen diep at xs4all.nl
Mon Nov 7 18:57:45 EST 2011


On Nov 8, 2011, at 12:44 AM, Joseph Han wrote:

> To further complicate issue, if latency is the key driving factor  
> for older hardware, I think that the chips with the Infinipath/ 
> Pathscale lineage tend to have lower latencies than the Mellanox  
> Inifinihost line.
>
> When in the DDR time frame, I measured Infinipath ping-pong  
> latencies 3-4x better than that of DDR Mellanox silicon.  Of  
> course, the Infinipath silicon will require different kernel  
> drivers than those from Mellanox (ipath versus mthca).  These were  
> QLogic specific HCA's and not the rebranded Silverstorm HCA's sold  
> by QLogic.  (Confused yet?)  I believe that the model number was  
> QLogic 7240 for the DDR version and QLogic 7140 for the SDR one.
>
> Joseph
>

Claim of manufactuer is 1.2 us one-way pingpong for QLE7240. Of  
course to get to that
number possibly they would've needed to use their grandmother  
analogue stopwatch,
but even 1.2 us ain't bad :)

95 dollar on ebay.

Anyone having even better news?

Vincent

>
>
> Message: 2
> Date: Mon, 07 Nov 2011 14:21:51 -0600
> From: Greg Keller <Greg at Keller.net>
> Subject: Re: [Beowulf] building Infiniband 4x cluster questions
> To: beowulf at beowulf.org
> Message-ID: <4EB83DDF.5020902 at Keller.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
>
> > Date: Mon, 07 Nov 2011 13:16:00 -0500
> > From: Prentice Bisbal<prentice at ias.edu>
> > Subject: Re: [Beowulf] building Infiniband 4x cluster questions
> > Cc: Beowulf Mailing List<beowulf at beowulf.org>
> > Message-ID:<4EB82060.3050300 at ias.edu>
> > Content-Type: text/plain; charset=ISO-8859-1
> >
> > Vincent,
> >
> > Don't forget that between SDR and QDR, there is DDR.  If SDR is too
> > slow, and QDR is too expensive, DDR might be just right.
> And for DDR a key thing is, when latency matters, "ConnectX" DDR is  
> much
> better than the earlier "Infinihost III" DDR cards.  We have 100's of
> each and the ConnectX make a large impact for some codes.  Although
> nearly antique now, we actually have plans for the ConnectX cards  
> in yet
> another round of updated systems.  This is the 3rd Generation system I
> have been able to re-use the cards in (Harperton, Nehalem, and now
> Single Socket Sandy Bridge), which makes me very happy.  A great
> investment that will likely live until PCI-Gen3 slots are the norm.
> --
> Da Bears?!
>
> > --
> > Goldilocks
> >
> >
> > On 11/07/2011 11:58 AM, Vincent Diepeveen wrote:
> >> >  hi Prentice,
> >> >
> >> >  I had noticed the diff between SDR up to QDR,
> >> >  the SDR cards are affordable, the QDR isn't.
> >> >
> >> >  The SDR's are all $50-$75 on ebay now. The QDR's i didn't  
> find cheap
> >> >  prices in that pricerange yet.
> >> >
> >> >  If i would want to build a network that's low latency and had  
> a budget
> >> >  of $800 or so a node of course i would
> >> >  build a dolphin SCI network, as that's probably the fastest  
> latency
> >> >  card sold for a $675 or so a piece.
> >> >
> >> >  I do not really see a rival latency wise to Dolphin there. I  
> bet most
> >> >  manufacturers selling clusters don't use
> >> >  it as they can make $100 more profit or so selling other  
> networking
> >> >  stuff, and universities usually swallow that.
> >> >
> >> >  So price total dominates the network. As it seems now  
> infiniband 4x is
> >> >  not going to offer enough performance.
> >> >  The one-way pingpong latencies over a switch that i see of  
> it, are not
> >> >  very convincing. I see remote writes to RAM
> >> >  are like nearly 10 microseconds for 4x infiniband and that  
> card is the
> >> >  only one affordable.
> >> >
> >> >  The old QM400's i have here are one-way pingpong 2.1 us or  
> so, and
> >> >  QM500-B's are plentyful on the net (of course big  
> disadvantage: needs
> >> >  pci-x),
> >> >  which are a 1.3 us or so there and have SHMEM. Not seeing a  
> cheap
> >> >  switch for the QM500's though nor cables.
> >> >
> >> >  You see price really dominates everything here. Small cheap  
> nodes you
> >> >  cannot build if the port price, thanks to expensive network  
> card,
> >> >  more than doubles.
> >> >
> >> >  Power is not the real concern for now - if a factory already  
> burns a
> >> >  couple of hundreds of megawatts, a small cluster somewhere on  
> the
> >> >  attick eating
> >> >  a few kilowatts is not really a problem:)
> >> >
>
>
>
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