Video fills a Mac faster than anything else, and most of it is derived

Video is the fastest way to fill any drive, and the ratio is worse than people expect: for every gigabyte of footage, an editing workflow can produce two or three more in proxies, render caches and exports, none of which is irreplaceable.

The five categories

The setup

1. Footage on an external drive organised per project, with a second copy before you start editing.
2. Cache and proxies on the fastest drive, which is usually internal, and cleared when the project is done.
3. Project files on the internal drive, small and backed up constantly.
4. Exports deleted after delivery, keeping only the final master.
5. Archive per project, stripped of everything derived, per archiving old projects.

Cache locations to set once

# Resolve: Preferences, Media Storage
# Premiere: Preferences, Media Cache
# Final Cut: Library properties, Storage Locations

Every editor lets you choose where cache and generated media go, and every editor defaults to somewhere on the internal drive. Changing it once per application is the single most effective thing on this page, and it is covered per tool in Resolve's cache and Adobe's media cache.

When the disk fills mid edit

That is usually cache rather than footage, and clearing render cache inside the application is safe and immediate. The urgent version, when an export fails partway, is in cannot save because the disk is full.

The number worth knowing

A project's derived data is routinely three to ten times the source footage. That means a 200 GB project folder can archive to 30 GB with no loss of anything you cannot regenerate, which is the arithmetic that makes archiving worth the hour it takes.