Select your VM. Select "Guest OS" on top/left. In the next window you should have the VM Flags tab at the extreme top/right to be selected. At the bottom you should then have the option to select the best policy for the cache, to OS X or to the VM.
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Correction: you do not have the option to disable OS X's cache but the option to assign a better policy to the VM's cache.
Last edited: Aug 15, 2006