Thanks Randy. Yea, I have some USB docked drives that I use for off site backups. Well, their in the cupboard in another room:) That may well be the way to go. It's just sloooow..
 
Speaking of slow, I'm transferring (copy/paste) around 300 gigs between these Samsung SSDs and they are copying at only 50 mb/s.. That seems kind of slow to me.  Anyone reading this know?? I thought these things were supposed to do  6 gb/sec.
 
edit:
woops, the transfer is (was) between a regular HDD and an SSD. ran around 57mb/s.

I have removable drive bays on the desktop.
 
My laptop has SSDs. PCIe is a lot faster than SATAIII. My SSDs are SATAIII though my system supports both.
 
Apparently M.2 laptop SSDs don't come with a mounting screw so you'll need to add that when buying one. They are M2 x 3mm.

Not sure if this helps since you're asking about internal HDs, but I'll throw it out there anyway.
I have three external USB hard drives and each one is plugged into a 6 outlet power strip with
individual switches.  When I need one of the HDs I just flip the switch for that one drive.

For example:

https://www.amazon.com/OU...-Generic/dp/B002YKPWH0