Building redundancy

[Ashley M. Kirchner]

    First, the question: How to build redundancy on a "users" server?

    What's behind it: When our main users server goes down, no one can 
log in to check their e-mail.  So the problem as it was presented this 
morning was to research some way to make it so that if that server goes 
down, users still have a way of getting to their e-mail or login to 
their accounts for that matter.  Now, the setup we have is a bit 
different from most people I'm sure.  Incoming e-mail flows as follows:

    Internet -> MX server -> spool server (NIS+ slave)

    Our "users" server - also our NIS+ master - (which is a totally 
different machine) does an NFS mount of the spool server on /var/mail/ 
and voila, e-mail.  When our users use imap/pop to check/get/send 
e-mail, they log in to that "users" server to do so.  No one 
communicates directly with the spool server.  So when the "users" server 
goes down, no one can get to their e-mail.  The question: what kind of 
redundancy can I build so that if that server were to go down, that 
users can still log in (to -something-) and still access everything they 
need.  Presumably this would be a separate machine and that the fall 
back would be transparent to them.  I just don't know how or what.

-- 
H | I haven't lost my mind; it's backed up on tape somewhere.
  +--------------------------------------------------------------------
  Ashley M. Kirchner <mailto:ashley at pcraft.com>   .   303.442.6410 x130
  IT Director / SysAdmin / WebSmith             .     800.441.3873 x130
  Photo Craft Imaging                       .     3550 Arapahoe Ave. #6
  http://www.pcraft.com ..... .  .    .       Boulder, CO 80303, U.S.A.