zfs is an option … just the legality of it is questionable. But it would address a lot of people problems. (Thou let’s not forget that zfs raidZ (5,6, and this triple parity thingy) does not allow single disk addition to the pool so the “normal people” that can afford to buy one disk in few months are f**** :* good luck !
Also, 10TB disks are different animal all together. Due to write technology used on those, they don’t write in single sector type of fashion but in “fields” where updating part of data overwrites other part of data, so update have to read a massive amount of data (2MB and more !!!) then write it down in once.
So if you have a non sequential IO (gosh, let’s say a metadata update) you will “seek the disk to death”. Seagate doesn’t care because on paper their hdd looks blazing fast, in reality you get a punishing seek performance. Of course btrfs 30second in memory data check pointing helps but still far from ideal. Zfs has a solution for it with ssd cache - but there are people poping up complaining that failed SSD destroyed whole array ( not to say that bcache and btrfs are any more stable / reliable … their not … I would not use this combo for holding my pron backup ) Again FUN !
Those 10TB disks are designed for “cold storage”, where you don’t modify your data at all, just add to it. Btrfs (AND ZFS) was designed for people that actually use their storage & modify stuff - that’s why there are rockon’s here that work pretty well (freenas has their chroot jails and those deliver too !). Imagine putting a owncloud on one of those 10TB disk ? OC got mysql backing store - this pushes data down to disk in very random pattern, plenty of it will get hidden in extents due to small size … this results in more random pattern … FUN !
Somebody did a fantastic comparison on freenas page which clearly points out how many active developers are there in each project ( I think for btrfs it was 2 ). So if RAID 5 & 6 is such a deal breaker for you guys … come up with something ! There is a full proof written tutorial how to contribute some code (even I could follow it), help to get some of burning issues out of the way and mesh up something that allows simple pool creation in ZFS and we’re golden ! We may even convince all freenas people to come to us and abandon their project, right? ( could not resists some good old sarcasm )