Scratch disk

To create a scratch disk:

You need to configure Final Cut Pro so it will find the drive and the project folder where you will be capturing your video clips and creating your Final Cut Pro movie. The drive and project folder are called your "scratch disk," which could be a portable firewire drive on which you are storing all your video files.

1) Start Final Cut Pro.

2) In the menu at the top click on Final Cut Pro... System Settings

3) Then select the tab for: Scratch Disk Settings

4) Near the top of the screen that appears you'll see a series of checked boxes for Video Capture, Audio Capture, Video Render and Audio Render.

These should be checked so you can set all of them to the scratch disk drive and folder for your project (so when you capture your video and audio it will be stored in the right folder, and when you do rendering of your movie it also will be stored in the right folder).

5) To the right of those click on the button labeled Set and navigate through the computer's directory to your scratch disk drive. If you already have a folder for your project, just click on it. If you don't have a folder, then click on the New Folder button to create one and give a name to it.

For example, if you're using a portable firewire drive, click on Set and Choose a Folder to find the icon for the firewire drive on the desktop and open it.

6) You should now be back at the Scratch Disk Settings screen. This time look further down on the screen for the other three buttons labeled Set:

Waveform Cache Set

Thumbnail Cache Set

Autosave Vault Set

These are three other Final Cut Pro settings, each of which also should be set to the same scratch disk as the first one.

It is especially important that you set the Autosave Set button to the same scratch disk, as this is where Final Cut Pro will periodically save copies of whatever you're working on so you don't lose your work if the computer crashes. You want to be sure that these automatically saved files are being saved to your scratch disk drive and folder.

Make sure all three Set buttons have been set, and follow the same directions as above to useChoose a Folder to set each of these to the same scratch disk.

When you're done and back at the Scratch Disk Settings Screen, leave the default settings for the other options, such as Minimum Allowable Free Space on Scratch Disks, Limit Capture...Size and Limit Capture Now.

And click on the button at the bottom labeled OK. Now start a new project in Final Cut Pro by clicking on File...New and click on Save Project As... Give your project file a name and then navigate through the directory tree to the same scratch disk drive and project folder you used in the Scratch Disk Settings instructions above. Save the Final Cut Pro project file in that folder.

Once you've completed these settings, they are now stored in the copy of Final Cut Pro on the computer you're using.

The next time you launch Final Cut Pro, it will look for that scratch disk. If someone else has used that computer in the interim for a different Final Cut Pro project, they probably set it to use a different scratch disk. In that case at the prompt you'll need to reset the scratch preferences to your disk, as described above.

Why Scratch Disks Are Important:

Whenever you use your computer, your operating system frequently writes and retrieves information from a swap file on your main hard disk. The swap file is a temporary file that is created to help speed processing and applications and as a virtual replacement for RAM memory. Because not all data requires the speedy processing available with RAM memory, your computer is able to use a swap file for caching files that are not so processor intensive.
This means that data is constantly being written and retrieved from your computer's main hard drive. Because your computer's primary hard drive is used so much, it is not a good candidate as a scratch disk in Final Cut Pro. Rendering and other techniques used in video editing require a lot of processing power, and processes and other data actions occurring on the main hard drive would prevent efficient and timely rendering in Final Cut Pro. Thus, Final Cut Pro requires that a separate scratch drive be used for rendering and editing.