I ran a FreeBSD ZFS NFS server for a cluster for quite a while. I loved it. It was simple and stable. The thing that led me away from FreeBSD (aside from IT not being happy with an "alternative" OS), was that I needed a clustered filesystem. We outgrew the stage where I was comfortable with a single node and where upgrading storage meant a new JBOD.
Are there any FreeBSD-centric answers to Ceph or Gluster or Lustre or BeeGFS?