[BlueOnyx:05255] Re: Secondary mail server

[Chris Gebhardt - VIRTBIZ Internet]

Hi Gary,
Be very, very careful with your configuration.  Long story short, 
though, you can save yourself the trouble of setting up another box to 
test with.

> If two BlueOnyx environments are set up with the same domains/vsites and
> users (but different IPs obviously), but I configure the Secondary Mail
> Server in one to point to the other, will that take precedence over the
> usual mailbox delivery on that particular server (in the case the other
> one is down)?  

This is NOT how it works.  If you just configure 2 BX boxes, then they 
will both just assume that they are authoritative for the domain.  You 
can configure one as a primary and one as a secondary MX if you want, 
but that won't really do what you're thinking it will, either.  What 
you'll wind up with is mail "randomly" ending up on one box or the other.

> I'm thinking about loading two servers from the same
> cmuexport, and using them for load balanced web serving, but just having
> mail delivered to one box with the other available as a backup mail server

Save yourself time and trouble.  Don't do it.  Rather than putting up 2 
servers for "load balanced web serving", just put up one server that's 
robust enough to handle the load.  If the site is busy / important, make 
sure you're not hanging a monster server off a DSL or T1 line and put it 
  with a facility that is robust enough to support the traffic.  It 
always amuses me when folks put in monster dual-quad core servers with 
12GB RAM so they can do their own server on a DSL line.  Whoops!

But back to point, what will wind up happening, again, is that you'll 
have email going "randomly" to both servers that you've set up.  In 
addition, assuming you're using round-robin DNS to resolve your WWW to 
either server, you're going to have inconsistent logging, sessions that 
don't carry across and databases that are not synced up.

If you want to use 2 servers for redundancy, then configure them in a 
cluster.  Aventurin{e} makes this drop-dead simple.  Or you could roll 
your own cluster using Linux heartbeat clustering, some rsync and some 
MySQL replication.   I've worked both ways.  For my time and money, 
Aventurin{e} is the way to go.  You just set it up and it works.

> - I'm guessing sendmail will end up with configuration for the vsites as
> well as the secondary mail server, but in the event of the main server
> failing will mail queue up waiting to be delivered to the main server (as
> I'm hoping), or will it be delivered to the redundant mailboxes on the
> secondary server?

Yes, I can see how you'd guess this but it isn't at all the way it will 
work out.   Just setting up another server with an identical 
configuration will not give you the redundancy you're looking for.  It 
will give you headaches and heartbreak.

So by now you're asking "so what's that secondary mailserver box for if 
it doesn't do what I want?"   Ah.   Happy to explain.

What it's there for is in the event that you want to set up a secondary 
server that will queue your inbound email in the event that your primary 
system goes offline.  The idea would be that the secondary box will 
accept the email then queue it for delivery to your primary system as 
soon as it becomes available again.  That way nobody loses email during, 
say, a reboot or when the DSL line you're hosting your dual-quad 
mega-RAM, RAID-10 box peters out on you only to return whenever the 
telco gets around to it.   :)

I hope that helps sort it out for you.

-- 
Chris Gebhardt
VIRTBIZ Internet Services
Access, Web Hosting, Colocation, Dedicated
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