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I run 2 VMs. Those two VMs are not doing any CPU intensive tasks, and the host machine has a Sandy Bridge Celeron CPU, 8GB of DDR3 RAM and conventional HDDs. When I checked the CPU usage, it is not high, like 20~30%. Also the RAM is enough, I think.

But the VMs are really slow. Is it possible that even if the CPU utilisation percentage (measured in the host) is low, VMs run slow due to the CPU being a low-end (Celeron)? I have the money to buy a higher-end CPU like an i5, the only reason I chose a Celeron because I thought it would not read much power.

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How much ram and video memory have you allocated to each vm, and how much is left for the host? – MariusMatutiae Oct 17 '13 at 9:41
What is your host OS? and what are your guest OS's? What vm software are you running? The question @MariusMatutiae asked is very pertinent, and you should answer it before you get a meaningful answer. In my experience RAM is key. 8GB is probably not going to be enough. – Deesbek Oct 17 '13 at 19:47

What kind of VMs, are you running? In case you have HDDs, you should check HDD queue length first. You can check it in resource monitor of host machine (you can run it typing resmon in command prompt). If you see there 3 or more than you should consider separating each VMs' disks files on different disks.

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The answer to your question is most probably not.

VMs normally require RAM rather than CPU, however that depends on what you are doing and how you set them up in the first place.

Please answer my comment questions and I'll expand my answer?

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I suggest you also to watch the CPU Ready Time parameter of your VMs. Normal values are about tens or hundreds of miliseconds. Celeron is not very appropriate processor for virtualization and may be a reason of those lags. Although I agree with Deesbek, that slow HDD is the reason of your troubles.

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