Storage of video raw files

I store my original media in all three places, and all are double backed up -- i.e, stored on two separate drives. Of course, no way to avoid duplicates, but I believe in as much safety as possible. Preferences vary with the individual person.

You never want to have any app, iMovie or Photos app, be the sole places where you store your original media. Apps can become corrupt or obsolete. With iMovie, it is particularly awkward to organize and retrieve original media. iMovie libraries can become corrupted, as well. And with iMovie you may want to store only the media that you intend to use in your projects, the remaining media necessarily being stored elsewhere. The Photos app is great for organization, file management, and retrieval but it has been known to be somewhat quirky, causing some users to lose their photos and videos. Photos libraries can become corrupted. And the Photos app changes with every iteration of the operating system.

Redundancy (duplication) is the best safety precaution. In my view, you can never have enough redundancy. External storage is cheap. Unfortunately, even external drives fail after 3-5 years, and so I double back up, using at least two drives. Six months ago I was getting some strange error messages when using one of my external drives. Since that type of thing can be a forewarning of drive failure, I replaced the drive with a new drive.

-- Rich

Regarding deleting the original media from an iMovie project after one has finished editing it: Deleting the original media will delete it from the current project and all other projects that might be referring to it, thus disabling those projects so that you will not be able to export them. Once you have exported the file, then you can delete the project and original media if you want, as long as other projects aren't using it, although you then will be unable to go back and re-edit or export the project out again. Also, if iMovie is the only place where you have stored the original media, deleting it will cause you permanently to lose it.

The better solution is to store your iMovie library on an external drive that is formatted Mac OS Extended (Journaled) or APFS. Then you don't need to worry about space issues. If the library gets too large, simply create a new library in addition to the old one, and work from the new library. You can create as many libraries as you want.

-- Rich