Because the DNS-321 doesn't support NFS, I've had to use SMB/CIFS protocol to get my Linux laptop to use the NAS.
I first started by using the default SMB client filesystem support in Mandriva 2008.1, which is smbfs. This had lots of problems -- no POSIX filesystem semantics, and the mount hung frequently during high loads or concurrent access.
The solution is to make sure your Linux client is using the newer cifs filesystem client instead of the outdated smbfs. This also allows for POSIX filesystem semantics (mixedcase filenames, hardlinks, symlinks, permissions, etc), as Samba in the DNS-321 appears to have LinuxExtensions enabled. The line in my fstab looks like:
//192.168.1.90/drn /archive/drn cifs \
credentials=/etc/samba/auth.nas1.drn,uid=drn,gid=drn,_netdev 0 0
This seems to be very stable, fully functional, and has allowed me to continue using rsnapshot as my Linux backup solution.
-david