I use VMware Workstation on MS-Windows XP to run a number of virtual Linux machines. This has worked very well for sometime now.

Recently the virtual machines have been starting and running very slowly; taking anything up to 15 minutes to come up with the login prompt. This has been across the board on all virtual machines and had me stumped as ‘nothing had changed’.

Well, something did change, which I forgot about.

I upgraded my Diskeeper defragmentation tool to the latest release, Diskeeper 2008. A virtual machine uses a number of large files to simulate a virtual disk and these files can get significantly fragmented over time very quickly. I have found that defragging is almost essential to keep performance up for a virtual machine.

Previously the automatic defragging by Diskeeper in the background has never been a problem. But after turning the auto-defragging off, the virtual machines burst back into life again.

As I have all my virtual machines on a separate disk, I have left auto-defragging on for the main ‘C’ drive and I will have to do a manual defrag of the virtual machine drive very so often. This is not as bad as it sounds, I use the pre-allocated file configuration for all the important virtual machines so the fragmentation is lower.