While at VMWorld, I talk with Tony from LSI. We talk about their new technology that uses flash drives to create a cache in MySQL databases. When databases get taxed, the software will use the flash drive to cache data so the database does not slow down. The dynamic operation will make the move seemless.
Although you have a cached version, you are still technically working on the main database to keep validity. When done, the cache with dump and the next bit of data will get queued. This is a write-through model.