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A license restriction limits us to 2 x dual core servers, or one 1 x quad core server.

  • Should we see better performance running 2 x Dual Core servers or 1 x Quad Core?

  • Dual Core processors are harder to find now. Which would give best performance?

EDIT Thanks for the responses. The application runs Tomcat Java and performs XSL/XML transformations. Would there be core to core communications on a Tomcat, or is each request handled in a single thread/core? The servers we have at the moment are both Dual Core Xeon E3113 3GHz

EDIT The application handles a considerable amount of XML throughput which is a memory, CPU, and network intensive task. Under the hood it uses a combination of DOM, XPath and Xerces.

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What application is imposing this license restriction? –  ewwhite Jul 8 '13 at 11:35
    
@ewwhite it's a propriety application with very limited distribution. I would prefer not to name the application itself. It runs under Tomcat, calls remote APIs and performs XML parsing/XSL transformations on the responses. –  Recursieve Jul 8 '13 at 12:17
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3 Answers

Ah, whatever you do, consider age.

These days dual core are harder to find as they are older. That means slower, per core.

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There's a dual-core Haswell E3 Xeon just come out - damn slow but new, and there's a one year old dual-core E3 at 2.3Ghz that's only 17w TDP. I doubt that's what the OP's asking about though ;) –  Chopper3 Jul 2 '13 at 18:32
    
Current processor is Dual Core Xeon E3113 at 3GHz –  Recursieve Jul 3 '13 at 10:07
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If there are any core-to-core communications then you'll find that generally a quad-core will be faster, sometimes significantly so, than two dual-cores. The reason is that the bandwidth and/or latency between cores on the same die can often be very much faster than any external connections. That said you don't mention specific processors so you could be comparing a new fast dual-core CPU to a very old quad core but I imagine that's not the case.

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On the flip side, two dual-core servers will have twice the bandwidth to main memory of one quad-core server, other things being equal. –  David Schwartz Jul 3 '13 at 1:08
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and maybe twice the L2 and/or L3 cache, but that depends on the actual cpu model –  Luke404 Jul 8 '13 at 11:34
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Regarding memory - I disagree. Half of the memory will be accessible for one processor through another one, reducing access time (NUMA issue), which is very important. The topic is about efficiency. Quad core CPU's are more efficient with power, therm, latency, but might be less efficient in Max. supported memory. TCO is reduced. –  GioMac Jul 9 '13 at 9:21
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@ewwhite it's a propriety application with very limited distribution.

Well, in situations like this, where you have an application with an archaic licensing scheme, you're going to be limited in your options as hardware progresses. Dual-core CPUs are all but obsolete in the modern processor offerings from the major manufacturers. Quad-core CPUs are also less available as 6-core and 8-core dual-socket servers advance.

The way I usually approach this type of restriction is through virtualization. VMware, for instance, provides a nice option to specify the core/socket count for software licensing purposes.

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Another option is to limit the number of cores available to the operating system at the BIOS level. High-end servers allow you to disable CPU cores on modern processors. That may get you to where you want to be and still provide you the benefit of faster CPUs and compatibility with newer servers.

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@ewwwhite This approach makes a lot of sense. Rather than getting end of line dual or quad core servers, get a modern processor with accompanying benefits of larger cache/instruction sets etc. while keeping within license restrictions. –  Recursieve Jul 9 '13 at 11:29
    
@Recursieve Right, this is what the manufacturers intend for people to use. There are also ways to do this at the OS level. Check with your application vendor to see if this is acceptable. And please mark an answer! –  ewwhite Jul 14 '13 at 23:41
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I recently came across some software that prohibited you from doing this to reduce your licensing cost (legally, if not technically). It actually sounds like it might be the same application. I would recommend that you check the license terms carefully and also check for competing products (which is what we did, and we are happier with the competition, and saved money to boot). –  Dan Pritts Jul 15 '13 at 3:21
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