2006-02-19

Optimization for running VMWare VMs from a USB or other slow storage device

I love VMWare. Great product, innovative company. Recently had a minor problem after upgrading from Workstation 5.0 to 5.5, and wound up searching VMWare's knowledge base. Though I wasn't looking for this type of information at the time, I ran across an article that details a change one can make to a VM's configuration (.vmx) file that might improve performance. I haven't tried this yet, but plan on it the next time I have to move my VMs off of my laptop HD to an external HD (or *GULP* a network drive - yeah, yeah - I know).

Basically, VMWare uses a file in the VM's directory as a memory swap file. USB devices read and write data more slowly than internal HDs. So, VMWare uses a swap file on the USB device, and performance suffers. The suggested fix is to add the following setting to the VM's .vmx file:

mainMem.useNamedFile=FALSE

This tells VMWare to use the host system's HD to store the swap data.

The VMWare KB article is "Virtual Machine on USB or Other Slow Storage Device Runs Slowly".

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