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We have two identical servers with the following specs:

  • 4 sockets containing AMD Opteron 6172 at 2.10 GHz each of which have 12 cores
  • 64 GB RAM

One runs Windows Server 2008 R2 Standard, which therefore can use 48 cores and 32 GB RAM. The other runs Windows 7 Professional, which therefore can use 24 cores and 64 GB RAM.

I ran a single threaded performance benchmark and the Windows Server machine was 1.5 times slower.

Any there any suggestions as to how I can find out why Windows Server is so slow?

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...what are you doing with Windows 7 on such a machine?!? – Massimo Feb 20 '12 at 19:32

Soudns broken. I would stop using single threaded applications at that point and pull out a standard perforamnce test.

There is nothing in windows server that makes it slower by a large degree. Not sure what difference you saw - a "factor of 1.5" is not very clear. you mean 1 secod and 1.5 second on the server?

Pull the serers out, run cpu performance tests on both. YOu may find their performance is different. I see nothing on a stock server causing this.

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Yes, exactly that the time taken on the slower machine was 1.5 that of the faster one. – Mark Bryant Feb 20 '12 at 9:45
no, not realted to the opearting system. Check hardware to start. And load on the server without software running should be around 0 (small spikes to 1 oe 2%). Anything higher means check WHAT uses the cpu. – TomTom Feb 20 '12 at 10:03

You said the two servers are identical; then, you can try swapping the disks between them and have each one boot the other one's operating system; this would let you check if the problem is actually related to the system or to some hardware/firmware/BIOS issue.

If the problem actually depends on the system, then the next step would be performing two clean installations of Windows Server 2008 R2 and Windows 7, don't install or configure anything else on them and run your benchmark again. This would help ruling out drivers or software issues.

If the difference in performance keeps happening again... well, then this would get interesting.

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The time quantums are different. Windows Server has a longer quantum than desktop editions so that the desktop experience is more interactive.

Read page 406 onwards in this book:

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You were probably experiencing the cpu throttling as described in

Change your power profile to high performance in Power Management, then edit the PCIE Link State to moderate power saving and also edit the Minimum processor state in Processor Power Management to 5%.

This will give you the best cpu performance with balanced power saving.

I can't believe this is still happening with Haswell cpu with C1E/C3/C6 and Speedstep enabled in BIOS running default balanced power profile on Windows Server 2008 R. Hehe

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Windows Server doesn't have to perform better than Windows 7 in running such benchmark as it doesn't fully utilize the system resource. Because Windows Server has slightly different settings in process scheduling and memory management, it runs a little bit slower than a desktop edition of Windows for some applications which are optimized for desktop use.

But I don't think it should be 1.5x slower. Could you check the drivers installed on Windows Server machine? Some drivers may come with Windows 7 but not with Windows Server.

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Sorry,this is rubbish. When I start a single threaded application on a windows server it should use the complete processor. Actually I do that all the time. Windows Server has no higher overhead for that type of operation than normal. Drivers also make no sense - unlöess the app is IO or so driven. A pure processor loop does not get invluenced by drivers. ;) I do that all the time - mass data processing, single threaded each, starting 12 threads on a processor (with 12 hyper threads). – TomTom Feb 20 '12 at 19:43

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