Global Shared Memory and SCI/Dolphin

[Franz Marini]

Hello,

  being in the process of deciding which net infrastructure to use for our 
next cluster (Myrinet, SCI/Dolphin or Quadrics), I was looking at the 
specs for the different types of hw.

  Provided that SCI/Dolphin implements RDMA, I was wondering why so little 
effort seems to be put into implementing a GSM solution for x86 clusters. 
The only (maybe big, maybe not) problem I see in the Dolphin hw is the 
lack of support for cache coherency. 

  I think that having GSM support in (almost) commodity clusters would be 
a really-nice-thing(tm). 

  I know that the Altix family implements GSM, but the price point of even 
a really small system (4 x Itanium2 procs, 4 Gb ram, 36 Gb HD) is really 
high, compared to an (performance wise) equivalent commodity cluster. And 
I can really see that SGI had a nice ccNUMA hw already developed, and so 
the software effort to implement GSM has (probabily) been less massive 
than the effort a Dolphin GSM solution would need. 

  Nonetheless, I still can't quite understand why so little effort is 
being put in developing a GSM solution for commodity cluster (even with 
Myrinet or Quadrics, I'm thinking about SCI/Dolphin only because of the hw 
support for RDMA operations).

  Any idea, comment or whatever ? 

  Have a nice day everyone,

Franz




---------------------------------------------------------
Franz Marini
Sys Admin and Software Analyst,
Dept. of Physics, University of Milan, Italy.
email : franz.marini at mi.infn.it
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