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Cray CTO: Linux clusters don't play in HPC (Search Enterprise Linux)Cray CTO: Linux clusters don't play in HPC (Search Enterprise Linux)Posted Apr 13, 2004 19:48 UTC (Tue) by dcoutts (guest, #5387)Parent article: Cray CTO: Linux clusters don't play in HPC (Search Enterprise Linux) This isn't a Linux vs. the establishment thing, it's a shared memory vs. cluster argument. Cray could easily run Linux on their new shared memory supercomputers, it's just that for historical reasons they are using a (heavily modified) version of Irix (there has been some rumour of them changing to Linux in the future due to contractual issues over Irix). The CTO is just bad-mouthing the Linux clusters because that is the current competition. If they were old-unix clusters the argument would be the same. The point is really about hardware. Cray's shared memory machines are much easier to program for certian problems (eg old Fortran progs). Everyone agrees that for problems that can be suffieiently split up to run on a cluster with reasonable performance, that clusters are definately the way to go (which is why Cray will sell you a linux cluster). However there are certianly problems that cannot be split up to work on distributed memory machines with reasonable performance or problems where the effort required to rewrite the software is far too great. For example there are 1M LOC Fortran progs that have evolved continuously over 30 years where it is cheaper to buy an extremly expensive new supercomputer than to rewrite the software for a cluster. As far as I know, Cray's shared memory interconnect is still an order of magnitude or so better in terms of bandwidth/latency than infiniband/myrinet etc. The other major difference is that supercomputer CPU's have hundreds of general purpose registers and several kilobytes worth of vector registers. Disclaimer: I was an intern with Cray for 3 months several years ago.
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Cray CTO: Linux clusters don't play in HPC (Search Enterprise Linux) Posted Apr 14, 2004 6:51 UTC (Wed) by arasila (guest, #20891) [Link] Cray could easily run Linux on their new shared memory supercomputers, it's just that for historical reasons they are using a (heavily modified) version of Irix (there has been some rumour of them changing to Linux in the future due to contractual issues over Irix). This computer (Cray XD1) is a Linux system. Accoring to their own datasheet, the system is running "CRAY HPC enhanced Linux, Kernel version 2.4.21". The system seems to be some kind of NUMA system, quite similar to SGI Altix, but with AMD Opteron CPUs instead of Itaniums. So, the guy is just trying to differentiate their from self-made Linux clusters and not to make any Linux vs. UNIX argument.
Cray CTO: Linux clusters don't play in HPC (Search Enterprise Linux) Posted Apr 14, 2004 11:59 UTC (Wed) by dcoutts (guest, #5387) [Link] I meant they could run Linux on thier traditional style supercomputers as well as their new cluster style machines.At the moment, Cray have basically got two products: 'cluster style' machines (eg T3E,XD1) comprising of lots of off-the-shelf processors linked together with a proprietary interconnect to create a NUMA shared memory system. Their other type (eg SV1,SV2) are the more traditional machines with monster vector cpus in SMP nodes and linked together (NUMA) with Cray's proprietary interconnect. These are the ones that run Irix but could just as easily run Linux.
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