My OS is on a 512gb M.2 drive, but the main storage on my laptop was a 1TB HDD, it started making noise about 2 weeks ago so I backed everything up onto a 1TB SanDisk USB SSD. This afternoon it got very clicky when I booted it up after work and icons for a few games I had stored on it, like KSP and YUZU, disappeared from the desktop and taskbar.
It's a fair bit more than that, but yes in a sense it is RAID if you are using it across more than one drive (as you should). You can use ZFS on a single drive though, so it's a middle ground situation.
The main thing is to avoid hardware RAID controllers unless you have a really good reason, and that's generally what most people refer to as RAID. Generally folks are moving to JBOD setups with filesystems like ZFS now though
Ah well, I was not aware that people usually mean hardware when they say raid. Thanks for clearing that up.