I finally figured out why all of my virtual machines on my Windows Server 2008 machine were running slow.

2x Quad Core Xeon CPUs
8GB of RAM
Windows Server 2008 Enterprise x64

I have HyperV installed. I had 4 virtual servers installed, and I just installed another 4 today. They were running _very_ slow, so I thought to pause BOINC and see if that had any effect. As soon as I paused it the machines sped up _tremendously_.
So I have a replicteable issue on my server at the moment - if I run BOINC with SETI@HOME at the same time as my virtual servers they all crawl. Turn off BOINC and the servers are very fast.

Each of the 8 SETI@HOME processes are running at Low priority, and each of the virtual servers are running at Normal priority.

Any thoughts?

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I haven't familiarized myself with HyperV yet, but are there any add-ons that you have to install for your virtual machines? I don't know if HyperV is similar to MS's Virtual PC, but in order to prevent my system from being bogged down I have to install the Virtual PC Extensions software on each VM to keep things running smoothly. Could this be the case?

If there is insufficient RAM for all processes what you get is disk thrashing while windows fails in its attempt to keep all of the needed portions of all programs and data in RAM.

So, the obvious question is: When this happens, is the Hard Disk activity light on?

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BOINC WIKI

Thanks for your responses.

OzzFan; Yes, HyperV is similar to other virtualisation technologies, in that there is additional software you can install to improve the performance of the OS. Each of the installed servers have the software installed.

John McLeod; There's plenty of RAM free, and even if the machine was paging, it's paging to mirrored 15K RPM drives ;-) Each virtual machine uses 512MB of memory at present, so 4 of them running is only 2GB of the 8GB installed. The machine has about another 4GB cached, and the rest is free.


The machine is blindingly quick. It just seems that for some reason, HyperV ends up running some of its threads at low priority, at which point the majority of CPU time goes to SETI@HOME. That's the only thing I can think of...

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Thanks for your responses.

OzzFan; Yes, HyperV is similar to other virtualisation technologies, in that there is additional software you can install to improve the performance of the OS. Each of the installed servers have the software installed.

John McLeod; There's plenty of RAM free, and even if the machine was paging, it's paging to mirrored 15K RPM drives ;-) Each virtual machine uses 512MB of memory at present, so 4 of them running is only 2GB of the 8GB installed. The machine has about another 4GB cached, and the rest is free.


The machine is blindingly quick. It just seems that for some reason, HyperV ends up running some of its threads at low priority, at which point the majority of CPU time goes to SETI@HOME. That's the only thing I can think of...

OK. The machine has 8GB installed. Unless it is a 64 bit Windows install, the last 4.4GB are not being used. That should, however, leave plenty of room in any case.

If it is paging, the speed of the Hard Disk almost doesn't matter as it is still several orders of magnitude slower than the CPU and RAM.

You may be right about the super low priority threads, however, I have noticed that some Microsoft programs wait until the CPU is completely idle before allowing some threads to run instead of allowing the OS to do the scheduling. BOINC uses the lowest priority above idle. You might try Process Monitor from [http://www.sysinternals.com]Sys Internals{/url] (which is now owned by Microsoft, but still has good diagnostic tools available for free).

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BOINC WIKI

Yes I was going to use process monitor to try to figure out what's going.
The machine's running Windows Server 2008 Enterprise x64 - so it can address up to 2TB of RAM.
I'll try following this up internally in Microsoft too and see if anyone has any ideas there.

Thanks for your help so far guys.

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If Hyper-V has some threads at low priority causing conflicts with SETI's low priority apps, wouldn't BOINC's CPU throttling help resolve that issue?

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Yeah I suppose it would.... I'll give that a go!

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If Hyper-V has some threads at low priority causing conflicts with SETI's low priority apps, wouldn't BOINC's CPU throttling help resolve that issue?

Except BOINC's CPU throttling does not play well with multi CPU systems.

[edit]

Try dropping a CPU instead.

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BOINC WIKI