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I am looking to run between 6 and 8 virtual machines, each running Windows XP. Each virtual machine would run Magic Online (MTGO) and a few scripts for data sharing. The host itself would run nothing except a few scripts for data collection and parsing. The machine itself would be running 24/7 in a house environment. I have not decided on the virtualization software/environment but it will be something free (although the host OS might be Windows 7).

All things otherwise being equal, what should I look for in a desktop CPU to optimize performance in this scenario? Should I be looking for more cores or higher speed cores? Obviously a CPU integrating virtualization extensions will work better, but what about other factors? Are there other considerations I should take into account?

I have found very few recent benchmarks about virtualization, and none about multiple machine virtualization. I am looking for personal feedback of users with a similar setup and, preferably, benchmarks.

Found so far:

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Your host machine needs to have the right CPU, memory and disk to handle the load of each virtual machine and the host OS. Out of the box machines still need to be configured to the applications being run on them.

A single CPU quad-core machine should run 6 to 8 virtual machines if you have enough memory and manage the CPU partitioning and disk access. Two CPUs gives you more growth potential and lets you fall back to 4 to 6 VMs per host if you find the graphics processing too demanding.

Plan on 1GB to 2GB of RAM for each virtual machine. The host OS will need 512MB to 1GB or more (Windows 7 needs 2GB as either host OS or VM). The reality is that you should buy as much RAM as you can. Virtualization still places physical loads on the host and the machine will use all of the memory you give it. If you don’t have enough memory, disk swapping occurs which can drastically slow down the host.

The disk requirements depend on the apps you’ll be running. If they are low read/write applications and you’re not concerned with failure, a simple disk configuration will do. Lots of I/O and data integrity requirements may mean a separate hardware RAID unit.

Creating pre-allocated fixed disk partitions for your VMs will speed up the machine I/O since it doesn’t have to go through the effort of managing dynamic partitions. The trade off is more disk space gets used initially. Speed versus space is the tradeoff.

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