The ZFS code in illumos has gained another differentiator thanks to the hard work of Saso, who integrated LZ4 improved compression into our code base. This is a nice achievement, and enhanced compression should be quite useful for most applications of ZFS. If LZJB was always recommended to be turned on (it was by our team at least!), then LZ4 is even more recommended, unless all of your data is totally incompressible. (Most data is highly compressible.) You should check out his wiki post above, which contains a lot more details about the work, including some benchmark data.