Running Parallels VMs from a NAS As I don't have enough internal storage space on my MacBook Pro, I used to store my Parallels VMs on an external 500 GB HDD connected via Firewire 800. However, that drive eventually died, and I replaced it with a 3 TB Western Digital NAS.

Now, my Parallels VMs run extremely slowly. Actually, to be more specific – they seem to run at normal speed, but take forever to respond to UI inputs (e.g., when I click a button, there's a 30 to 60-second wait before it responds. But once it does, the UI updates smoothly).

Is there anything I can do to speed up the UI responsiveness, or is this just a side effect of running the VMs off of the NAS?

I run three different Windows VMs (two Windows 7, one Windows 8), and they're all equally slow, so it's not an issue with just one VM. I also haven't changed any settings or anything else other than moving them from the old FW800 HDD to the NAS.
All three of your VMs are stored on your NAS, correct? I am not surprised that they are all slow. You are streaming tons of data over a network and expecting it to work as if it were being used locally.

Virtual machines perform a lot of disk IO. Using network storage for VHD files and other resources that are used by your VMs is not really a great idea if you need responsiveness. A lot of software has been developed to try and solve the issue of streaming VMs over a network. 

You may want to look into the many VDI solutions that are available if you really want to continue using your VMs over a network. Just a thought. 

If this is not a good solution for you, why don't you try keeping a small VHD locally with just the operating system installed on it, and then add the bulk of the storage onto the NAS? That way, the VM would boot/run as quickly as it should (locally), and the majority of your data would reside on the NAS (and be accessible from all VMs and the host OS).



Edit: unless you are connecting your NAS via SATA, in which case I am unsure of a solution to your issue. As soon as I saw "NAS" I thought of you streaming your VM images over a network...