It can be made reliable, but it requires the stars to align perfectly. It is brittle and can fail in many ways. It’s definitely not recommended without an unreasonable amount of faith in the NFS client, server, and network. When made to be reliable, it is likely to be slower than expected.
There’s a “don’t do this, but if you must, here are some tips” recommendation here in the forums.
CIFS/SMB is also a poor choice.
I’d strongly recommend keeping the Plex databases on local disks, even if the remainder of the Plex data directory is moved to a network location.
I agree that iSCSI is typically a better choice than direct NFS mounts for this purpose.
(Note that this only applies to direct NFS mounts. Another common scenario, virtual machine disk images located on NFS, works reliably.)
