Any issues with having Virtual Machine on external drive?


macrumors member
Original poster
Sep 1, 2009
I know that we can store the VMs (either Fusion or Parallels) on an external drive and launch from it.
But is the speed the same compared to the VMs residing on the internal HD?
Any downsides to storing it on external HD?
(My EHD is USB not firewire).


Staff member
Aug 16, 2005
New England
Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 3_1_2 like Mac OS X; en-us) AppleWebKit/528.18 (KHTML, like Gecko) Version/4.0 Mobile/7D11 Safari/528.16)

You are limited to the data throughput of the USB bus instead of SATA so it is slower, but if the apps you are running are not very disk intensive you probably won't notice.


Bill Gates

macrumors 68030
Jun 21, 2006
Running any sort of disk-intensive application such as a VM through a USB connection is going to be painful. It will be very slow when compared with using your internal drive. It will function the same in all other respects.


macrumors member
Original poster
Sep 1, 2009
works great!

I went and anyway moved my Parallels VM to the external USB HD.

I am happy to report that there is absolutely no difference in performance.
I tried suspend/pause/restart/start/shutdown on Parallels 5 and I get similar runtimes:
Suspend: 4sec
Resume: 12-14 sec
Restart: 60 sec
Pause: 2 sec
shutdown : 26sec

(Note: These are all averages from atleast 4-5 times)
They were exactly the same when the VM was on my Mini's HD.

Also I did other tests, like moving files around, browsing, playing Farmville on fullscreen, brought up some apps, Word/PPT and no discernible difference atall.

My HD is 7200 RPM WD 3.5in.

On an another note:
Parallels 5 is great in terms of speed as noted above.
But it is still quite buggy compared to VMware 3.0.
Lots of problems with switching between the ridiculously many modes, problems with resolution, unnecessary dock icons and the annoying double lines.
But I still purchased it since I dont use Win7 that much and prefer the speed and will live with some workarounds.
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