In the HPC crowd, I'm quite familiar with OrangeFS (aka PVFS2) which recently entered the standard kernel. I had a PVFS 2.7 cluster running for many years, 24/7 with decent reliability (it crashed a few times, but never lost data).

It works with RDMA, has a POSIX layer, and is roughly equivalent to Lustre in performance in my tests, but 1° is very easy to setup (compared to Lustre) 2° has NFS actually working.