For peculiar local reasons, we have some ZFS pools that have overallpool quotas (on Solaris 10 U5, so these are real full quotas). We justhad the first such pool fill up and it turns out that when this happens,ZFS has a somewhat undesirable bit of behavior:

$ rm tankdata
rm: tankdata not removed: Disc quota exceeded

(You can't truncate anything either. Not even root can remove ortruncate files.)

This does not happen if the pool has no quota and

There's a simple answer to the question of how many root passwords youshould have; clearly, you should have a separate root password for eachsystem. This answer is, shall we say, naive in most situations.

We can see why by asking the traditional security question of what theactual risks are of using the same root password on different systems,which is that an attacker who gets your root password from one systemcan then immediately compromise another. So the first situation whereit is mostly or entirely pointless