This entire space is littered with hard to use and/or flawed products. It's extremely difficult to get right. And even things like HDFS, which redefine the problem into something much much more manageable and with better semantics for distributed computing, have had their own issues.

Take, for example, my favorite storage system Ceph. As I understand it was originally going to be CephFS, with multiple metadata servers and lots of distributed POSIX goodness. However, in the 10+ years its been in development, the parts that have gotten tons of traction and have widespread use are seemingly one-off side projects from the underlying storage system: object storage and the RBD block device interfaces. Only in the past 12 months is CephFS becoming production ready. But only with a single metadata server, and the multiple metadata servers are still being debugged.

With Ceph, some of these timing issues are that the market for object store and network-based block devices are dwarf the market for distributed POSIX. But I bring it up to point out that distributed POSIX is also just a really really hard problem, with limited use cases. It's super convenient for getting an existing Unix executable to run on lots of machines at once. But that convenience may not be worth the challenges it imposes on the infrastructure.