2 single quad core servers vs. 1 dual quad core server performance

Posted on 2009-02-08
Last Modified: 2012-05-06
We have an application that is very cpu intensive and are installing a new hosting configuration.  The application was built with load balancing so it will run on multiple servers and we will add more as we add users.  Is there a performance difference with two servers with 1 quad core cpu each  or one server with a one dual quad core cpu?.  One of these will be our starting configuration for the calculation part of the appliaction.
Question by:bpadge
    LVL 69

    Assisted Solution

    I would think that data paths on a single chip would be faster than on two separate servers.  Not only that, but cost-wise, you are only paying for one server with all the associated components versus two.  See this thread
    LVL 3

    Accepted Solution

    It is extremely difficult to answer this question definitively.

    In short, ":It Depends".

    In Long, "It depends on a huge number of factors, the only way to be certain is to benchmark the different solutions (including combinations of settings and techniques)"

    If your goal is to achieve the fastest possible performance, then what expense are you willing to go to in order to achieve it?

    Improving performance nearly always involves
      1. Identifying the largest impediment to performance
      2. Removing/improving the impediment
      3. Repeat until you have enough performance,. or run out of money/time to make it better.

    Impediments to software performance may be Poor Algorithms,  Poor Design,  Poor Implementation.
    Impediments to hardware performance are often contention for a (comparatively) scarce resource.

    Other impediments include unexpected serialization, excessive communication etc.

    So, back to your question:  Dual Quads in one server,   or Two single quad server?

    If we can make a huge number of assumptions, we could come up with some rules of thumb:

    Scenario 1:
     1. Computation is the limiting factor
     2. The Heavy Computation involves small data sets (i.e. they will all fit in on-chip caches)
     3. There is very minimal communication between the cores (few critical sections, mutexes etc)

    In this situation, there is little to indicate that a Dual Quad won't work as well as a pair of Single Quads.  Make the decision based on cost.

    Scenario 2.
     1. Computation is the limiting factor
     2. The Heavy Computation involves large data sets (i.e. they will not all fit in on-chip caches)
     3. There is some communication between the cores (critical sections, mutexes etc)

    In this situation, a Dual Quad won't work as well as a pair of Single Quads as Memory Access will be the bottleneck.

    Scenario 3.
     1. Computation is the limiting factor
     2. There is a lot communication between the threads

    In this situation, a Dual Quad may work much better as a pair of Single Quads as the communication overhead within a single system is much lower than between multiple systems


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