The Solaris guys got a massive jump on the linux community when it comes to modern filesystems. BTRFS is pretty much a GPL catchup effort, with some internal disk structure improvements. It currently doesn't have dedup thou. The SSD caches are also being worked on for linux, but in a filesystem agnostic way via bcache, but still has a lot of work before its ready. ZFS is also very memory hungry with a recommended 1GB of ram per TB of disk space (in the pool). The other nice feature to both ZFS and btrfs is the copy-on-write snapshots, the mentioned above checksums which combine really nicely with RAID (thou btrfs doesn't have RAID5 or RAIDZ), and on the fly compression is pretty nice too. ZFS wont be a successor to btrfs, ZFS wont ever be integrated into the Linux kernel (licence issues, and Oracle started btrfs and havn't shown any indication of re-licensing it, if even possible). Without integration it will always be a second class citizen in Linux. So far there has been no work to port btrfs to other UNIX systems either. Been running / on my laptop on btrfs for about 9 months now and have been pretty happy with it, it still has a few issues to iron out, but its getting there. Thinking about moving my home fileserver to btrfs soon too.