As pointed out in the comments on that thread, be aware that essentially all of the negatives about ZFS boil down to FUD. In particular, upstream is emphatically not dead (the recent OpenZFS summit[1] was packed -- as was the hackathon the next day), which can be easily verified just by looking at the commits to illumos.[2] As for "well known data base [sic] degradation", all I can say is that we run ZFS as a backend for Postgres all over our public cloud -- both ourselves as part of SmartDataCenter[3] and Manta[4] and with high profile customers -- and we have not seen any ZFS-related performance issues. And please don't get me started on the Oracle-related FUD...
[1] http://open-zfs.org/wiki/OpenZFS_Developer_Summit
[2] https://github.com/illumos/illumos-gate/commits/master
[3] https://github.com/joyent/sdc
[4] https://github.com/joyent/manta