I have Windows 8.1 installed with Bootcamp on my MacBook Pro with an SSD.
When I want to test certain software, I use HyperV Virtual Machines in Windows 8.1 which is very fast when used on an SSD, but it didn’t take long before I had some disk space issues on the SSD.
Because all these lab Virtual Machines were Windows 2012 R2, differential disks can drastically help reduce the amount of disk space used on the SSD.
First install a Virtual Machine with the Operating System you want to use, in my case Windows Server 2012 R2.
Optionally you can install the latest Windows Updates.
When the configuration of the OS is finished, run Sysprep with the options Generalize – Shutdown.
Don’t start this Virtual Machine, instead it’s safer to delete this Virtual Machine, and save the Virtual Hard Drive to a safe location.
Now create a new Virtual Machine and choose to attach a Virtual Hard Drive later;
When the Virtual Machine is created, edit this Virtual Machine and add a New Virtual Disk.
Choose “Differential Disk”.
Create the new Virtual Disk
Choose the Parent Disk that has been sysprepped.
Click Finish to create the new Differential Disk.
When the new Virtual Machine is booted, the new Virtual Hard Drive is only about 800MB
This saves a lot of disk space for all my Lab Virtual Machines!!