I have a MacBook Pro using Fusion 6.0.3 and two almost identical virtual machines, one with Windows 8.0 and the other one upgraded to 8.1, both machines share a second virtual hard drive where most of the data is stored (only one VM is on at a time). They both have the same amount of RAM (4GB), same number of processors (4)
The same process (an internal app that makes heavy disk use) that takes around 50 seconds in 8.0, takes about 1.7 minutes in 8.1
In a previous test (don't have the VM anymore) I remember working around the problem by setting hard disk buffering to disabled in the Advanced settings but with the new VM I tried all three possible settings (Auto, Enabled, Disabled) with no difference in performance.
Is there any pending Fusion update that will fix this issue? I have seen other threads pointing to poor disk performance as soon as a VM is upgraded from 8 to 8.1
Regards,
JuanC