Castle-enhanced Cassandra is a 20 minute video comes from Berlin Buzzwords and was given by Eric Evans of Acunu.
Castle is a new FLOSS storage backend for Linux as a LKM. It's designed to work with the SSTables that Casandra uses for storage. It's a write-optimized storage system that's optimized to work with both rotational disks and SSDs.
It looks like a great project, and glad something like this is open source. It would be interesting to see of other projects can take advantage of this project. There are other NOSQL projects that, while not using SSTs, use similar write-append strategies.