Editing & Post-Production
Scratch disk
Also called: cache drive, working drive
Premiere, After Effects, Photoshop and DaVinci Resolve all write large temporary files as you work, and the scratch disk setting decides where those land. Point it at a fast internal SSD, separate from your media drive. Previews stay responsive, because the application then reads footage off one piece of hardware and writes cache to another.
The classic failure is leaving it on the system drive, filling that drive, and hitting the scratch disk full error mid-session. In Photoshop that stops you saving. Clear caches between projects, keep a decent margin of free space, and never point one at a network drive.