Ubuntu Server 13.10 is out, and with it comes the 3.11 kernel with production-ready Bcache and dm-cache SSD caching options. SSD caching can help speed up NAS devices significantly by allowing reads and writes to hit SSDs before slower rotational media.
Ubuntu 13.1o is considered a stable release, although it’s only supported for 9 months. The next release will be 14.04 LTS with 5 years of support.
Information about other server package updates in Ubuntu 13.10 can be found in the release notes.