ZFS still also have the issue of having to perform well. You have a point, but ZFS is still trivial compared to a proper distributed filesystem, and you could achieve the same reliability much easier than ZFS if you sacrificed the performance.
The ClusterHQ guys behind the FlockerHQ found this out the hard way [0]. Initially Flocker was meant to provide a container data migration tool on top of ZFS, now it is a front-end to more established storage systems like Cinder,vSan,EBS,GPD and so on.
Absolutely -- I didn't mean to imply that ZFS even comes close to solving the distributed parts of the problem, but rather that a distributed storage system does have to address the problems of putting bits on disk.
