I've read notices of no hard link support for the NFS name space in NW 6.x
but have no information regarding NW 5.1. Does NSS on NW 5.1 support
hard links in the NFS name space? Is such support dependent on the
version of NFS or NFAP (NFAU) being used (for exported filesystems)?

Just in case anyone knows: if indeed NW 5.1 NSS NFS supports hard links,
why would Arcserve 6.1 volume copy fail to preserve hard links?
(Experiment done as follows: source directory on a NW 3.12 traditional
volume, exported under NFS, test files include hard links; destination
directory on NW 5.1 NSS volume with NFS name space; copy completed; source
and destination reversed; destination directory erased; copy completed;
hard links not copied back to NW 3.12 TFS directory (can't say if they
were ever copied to the NW 5.1 NSS volume since NFSSERV.NLM is currently
not running and so can't export for examination on a unix box).