Suppose that you have a situation where you need transparent highavailability NFS for something that is read-only and updated onlyinfrequently. Instead of going to the expense and bother of settingup real shared storage, it's tempting to try to implement this bysetting up a number of fileservers with local copies of the filesystem,synchronizing it from a master machine with rsync , and then using aslight variant of the basic HA NFS setup .

Unfortunately, the tempting easy way doesn't work; you can't

The NFS protocol uses something called a 'file handle' to identifywhat file a given operation applies to; this is sort of analogous tohow a traditional Unix system internally identifies files by theirinode number (well, their device plus their inode number).

In theory a NFS filehandle is opaque and an NFS server can use anyscheme it wants in order to uniquely identify files. In practice thereare a number of constraints on how a NFS server can form filehandles,based on preserving as many Unix semantics as possible