It's an Xraid running 10.4.11
There is no concept of 'login' on an Xraid. An Xraid is a disk array. However, since you mention 10.4.11 I assume you're looking for users logged into the
server that the raid is connected to, correct?
In that case, how are users 'connecting'? There are various ways of connecting to a server (console, ssh, AFP, NFS, even HTTP) so you need to be more specific.
If you want to know which users have a shell running on the server, run the
who command in your own shell.
If you want to know which users are logged in via AFP, use Server Admin.
Other protocols may (or may not) have their own methods of determining 'login'.