Another File system I am interested in is GEFS - good enough fs (rather - "great experimental file shredder" until stable ;-). It's based on B-epsilon trees, a data structure which wasn't around when ZFS was designed. The idea is to build a ZFS like fs without the size and complexity of zfs. So far its plan 9 only and not production ready though there is a chance it could be ported to OpenBSD and a talk was given at NYC*BUG: https://www.nycbug.org/index?action=view&id=10688

Code: http://shithub.us/ori/gefs/HEAD/info.html