This article explains how to set scratch disk preferences in Final Cut Pro.

The scratch disk is a folder on a hard disk or other storage medium where the program stores its media source files, including captured video and audio and rendered files. Always use your fastest audio/video (A/V) disk drives as your scratch disks. For best performance, avoid setting the system hard disk as the scratch disk and do not use a disk that has virtual memory turned on.

To change scratch disk preferences:

• Open the Edit menu and choose Preferences, then click the Scratch Disks tab.

• Capture Audio and Video to Separate Files: when on, video and audio are saved separately, which allows for better performance during playback and capture. To save audio and video files separately, you must specify a different disk for each (no tincluding the system disk).
• Video, Audio, Render storage: the disk or folder where video, audio, and rendered files are stored; specify more than one disk for increased storage space. The program automatically uses the specified disk with the most space available (rendering) or the next disk listed (capturing) when the current disk runs out of space.
• Waveform Cache: the folder or disk for waveform cache files (graphical representations of audio signals)
• Thumbnail Cache: the folder or disk for thumbnail cache files
• Minimum Allowable Free Space on Scratch Disks: when disk space falls below this minimum, the program will use another specified disk