I'm contemplating setting up my MacBook Air as a video editing machine. If I do this, I'll upgrade to a 256 GB SSD, and I should be able to keep around 100 GB or more free for video editing. The video files would of course be stored externally, but save purchasing some expensive Thunderbolt RAID device (which I suppose is gradually becoming more of an option), it will be slow for read/writes.
How can I have a set up where I take advantage of my SSD's speed for a scratch disk/cache for FCP X, but still have the TB(s) of storage of externals? I don't want to have to be moving files constantly back and forth, this is about saving time not wasting it.