I have a Samsung Evo 850 120gb SSD, as well as a 500gb HDD for storage.
Today, I've acquired a Patriot Scorch M.2 256gb SSD and plugged it in. The OS remained in my old SSD, and that's where I'm booting. I'm still not sure if I'll move the OS to the new SDD or use it only for gaming.
In any...