lwalkup :
What kind of storage should I use for a virtual machine workstation for learning and testing software like operating systems and networking tools? And would hardware RAID be beneficial?
Any type of drive.
I have a couple of my VM's stored on an SSD, and also some in HDD's in a NAS box.
RAID? Depends on what type, and what you're using these for. Just for learning, not really needed.
You do need a backup, as with ALL of your data.