You will need the available disk space on the Mac side but with 500GB – 1TB drives the norm, that’s usually not a problem and if you ‘re running on a Mac Pro, I’d guess a few dozen gig isn’t a huge issue for you either.
Apparently you need 20GB of free space for this particular transition and I had 19GB.
Unlike a real, physical disk, virtual disks have a really cool capability: you can just make ’em bigger whenever you want! I encountered an issue with upgrading to the preview edition of Windows 10 on one of my Mac systems too – also with VMWare Fusion – and was surprised to find that I had insufficient disk space to apply the update.
