[Linux-cluster] Postfix under cluster suite

[Lon Hohberger]

On Wed, 2006-03-08 at 13:35 +0100, carlopmart wrote:
> Hi all,
> 
>   Somebody have tried to setup a postfix cluster service under RHCS 4? 
> Is  it possible to mantain two postfix instances (one for node and 
> another to the cluster)?

I have not tried it, and I am not familiar with configuring Postfix in
the least, but here are some hints and gotchas which might exist ;)

* Both instances will want to (by default) bind to INADDR_ANY.  The two
instances must be binding to specific IP addresses - i.e., one instance
must bind to the host's IP, the other to the cluster floating IP - in
order for two instances to start in the first place.

* Both instances will want to deliver stuff in /var/mail ... and email
readers want to read from /var/mail.

Maybe the "RightThing(tm)" to do is something weird like the following.
This is a complete shot in the dark... ;)

- Cluster-mounted /var/mail (either GFS or not, it shouldn't matter)

- Node-specific Postfix instances never deliver mail directly, but
rather, they both forward to the cluster-instance Postfix IP.

- All postfix instances may accept mail for sending off-site.

This way, you don't have two instances of postfix both trying to manage
the contents of /var/mail (do they play nicely together?), all instances
of postfix can send mail, but only one does the ultimate receiving of
mail.

Also, if you use GFS for /var/mail, you may be able to run imapd on
multiple cluster nodes, but I've never tried this either.  As long as
multiple people aren't accessing the same imap mailbox, I am guessing it
would "just work" (famous last words, I know ;) ).

-- Lon