Global filesystem

A global filesystem is one which guarantees that the same path name corresponds to the same object on all computers deploying the filesystem. That implies

#usage of a global network
#prohibition of host-dependent mountpoints

Such filesystems are few and not widely known but they exist.

One (and in practice the only true) example is Coda.

A very close to global filesystem is Dfs. Its namespace contains both a global part and host-dependent shortcuts.

Another similar filesystem is AFS. Despite the similarity it does not qualify as a global one because the names under /afs are indirectly defined by the local host administrator.

Of course, it is still possible to use a global file system in a non-global fashion on a certain host or hosts, say by making a non-standard mount or setting up a specially crafted firewall.It makes the globality unavailable for the isolated hosts, but only for them.

In contrast, a filesystem which explicitly depends on each host administrator's decisions (mounts) can never be used without strict steering, which is impossible across administrative borders. With other words, it precludes any globality.