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What Do You Need To Watch For In A Linux SMP System?

Posted by Cliff on from the two-procs-is-almost-always-better-than-one dept.

thefin asks: "My research group has finally received funding (~$200K) for a single SMP box. I've looked over the offerings from SUN, IBM and Compaq. I was wondering what others think of the SMP offerings and in particular, opinions of Linux as a SMP OS. What should we know before purchasing such a machine? What should we look for and what should we avoid? We will be using the box for large, individual based ecological modeling efforts. These models are CPU intensive, and make heavy use of inter-node communications. In particular, inter-node communication can be a serious bottle-neck in our models."

4 of 23 comments (clear)

  1. distributed by milgram · · Score: 3

    Why are you buying a single box? Is it necessary? You can find a lot of information about distributed computing at the aggregate. You could use the money to build a computer as fast, and have computers to use for other things when the computer is obsolete (6 months). :)

  2. Ho-hum by Aunt+Mable · · Score: 3
    Firstly, imagine a beowulf cluster of these.

    Secondly, if internode communication is as high as you say and you can't parellelise your code/algorithms you made a good choice with SMP (as opposed to beowulf). Avoid x86, go for Alpha. Avoid Linux or *BSD, go for the native OS which scales to multiple CPUs much better.

    If you can parrellelise your code the obvious thang is beowulf and cheap x86 boxes.

    -- Eat your greens or I'll hit you!

    --

    -- Eat your greens or I'll hit you!

    1. Re:Ho-hum by Aunt+Mable · · Score: 3
      To avoid the troll calling: Linux and *BSD are good on x86 but in SMP they don't compare to Alpha's official OS.

      -- Eat your greens or I'll hit you!

      --

      -- Eat your greens or I'll hit you!

  3. Consider particularly Alpha and SGI by MemRaven · · Score: 3
    And ignore Linux. This seems to be a free-from-zealots conversation, so let me point out that for $200k, you're buying a LOT of CPU. Linux won't scale to the levels of CPU that you're getting. The use of signal-level threading and other kernel details limits linux on a really big SMP box.

    SGI's systems are really designed for this. The NUMA architecture is a way to mix what you're doing (i.e. lots of cpus, lots of memory) with the ability to make some things "closer" to others. If you're able to think of your app at least slightly NUMA like, it works well.

    Otherwise, let me recommend the Alpha boxes. Tru64 UNIX is a phenomenal operating system, and it scales beyond your imagining. It really is that good.

    The other thing to think about is what kind of CPU usage are you doing. Assuming that you're using floating point computation, you need to immediately discount the Intel architecture. It's STILL hobbled by the terrible FPU that it's had for years, which is why the Athlon kicks it around on this stuff. Alpha and MIPS have the best FPUs implmented (SPARC is okay, but definitely not as good as the Alpha).