Introducing Network File System Version 4 on HP-UX 11i v3
16
Additional Features in HP-UX 11i v3 ONCplus B.11.31.03
HP-UX 11i v3 ONCplus release 11.31.03 provides support for the following additional NFSv4
features:
• Cross Mounts
• Referrals
• Delegation Stackable Module for Local Access
Cross Mounts
The NFSv4 protocol allows clients to seamlessly traverse the server’s shared directories and cross the
physical file system boundaries on the server without having to explicitly mount each shared file
system independently. For example if the server is sharing the two file systems "/" and "/a/b"
respectively, the client, after mounting the root file system of the server, can traverse the file system
"/a/b" on the server without mounting the file system explicitly.
In prior releases an NFSv4 client was unable to traverse different file systems on the server by
crossing the file systems’ boundaries. The client was required to mount each of the server’s shared file
systems separately. HP-UX 11i v3 ONCplus version B.11.31.03 enables this functionality on the
client. The client detects the crossing of the physical file system by checking the ‘fsid’ attribute returned
by the server against the ‘fsid’ of the server’s file system stored during the mount.
The functionality overview of the client crossing file systems on the server is shown in Figure 16.
NFSv4 protocol does not require a MOUNT protocol to provide the initial mapping between path
name and filehandle. The server provides a ROOT filehandle that represents the logical root of the file
system tree of the server. In Figure 16, the server provides the pseudo filesystem with the root
directory “/” as a place holder to represent the top of the file system tree and to fill in the gaps in the
path names between real filesystems.
In Figure 16, the server has shared two file systems and the client mounts the server’s root file system
onto “/mnt” via NFSv4. With the cross mount functionality, the client is able to traverse, lookup and
access the contents of both the server’s file systems without mounting them separately. Note that the
client can alternately mount the server’s “/a/b” file system directly and then traverse into the
“a/b/c/d” file system.