Note that ZFS began development in 2001, not 2005, so ZFS itself isn't a new filesystem designed after 2005. The ZFS source code was first released in 2005, but

Note that ZFS began development in 2001, not 2005, so ZFS itself isn't a new filesystem designed after 2005. The ZFS source code was first released in 2005, but it was announced a year prior. In any case, ZFS is actually somewhat older. To turn your question around: what new serious [1] filesystems have been designed since 2005 (or 2001) at all, regardless of adoption? I think that the answer is actually far less than a few dozen. I can think of four: ext4 (as mentioned), F2FS (announced 2012, started ?), btrfs (started 2007), and ZFS (2001). Maybe there are others, I don't know, but I don't really think there are even that many contenders for adoption. (If there are, I'd be interested to find out). [1]: By serious I mean in a sense similar to what is outlined here: http://utcc.utoronto.ca/~cks/space/blog/linux/SystemdWhyItWon http://utcc.utoronto.ca/~cks/space/blog/linux/SystemdWhyItWo... in particular "In specific, none of these alternate init systems did the hard work to actually become a replacement init system for anything much", but for filesystems instead of init systems. For example, I would not consider HAMMER to be a 'serious filesystem' for the purposes of this list, whatever its technical merits.