"Note Customers are responsible for both defining and maintaining adequate network and disk I/O. Microsoft will not assist in troubleshooting slow performance due to networked .pst or .ost files. Microsoft will only assist if the performance issue is reproduced while the .pst or .ost file is located on either a hard disk that is physically attached to the computer that is running Outlook, or on a virtual hard disk (VHD) that is attached to the virtual machine that is running Outlook.
Important Microsoft programs may not work as expected in a third-party application or software virtualization environment. We do not test Microsoft products that are running in third-party application or software virtualization environments. For more information about support provided by Microsoft for its software running together with non-Microsoft hardware virtualization software"
has to be local not sitting on a share even for rdsh. the conditions above that are considered supported have to be sitting on a vhd that's attached.