Ok, some of this is above my head (which obviously needs to be resolved
:) ), but maybe i can clarify more here.
> For inbound SMTP you don't need a load balancer or layer 4 switch, simply
> use multiple MX entries. Let the DNS do the "load balancing" and let the
> sending MTAs figure out when a server isn't available.
>
> If you have internal people sending to SMTP servers, that's a case that
> can benefit from a layer 4 switch*.
>
All of these smtp servers will be on an internal network, with one
ipaddress at port 25 pointing to the round robin machine to the internal
machines. So the Mx record points to the the one public ip, and that
forwards to one of many 10.1.1.* addesses which handle mail. This system
has a limited number of external ips.
>
> Unless you are doing this for functional seperations reasons, I don't see
> a lot of benefit. If it's to have multiple queues on multiple spindles, why
> not stripe the file system? If it's that you are able to handle higher
> concurrencies than 250 I can understand. I would not do something like this
> unless you had a very real reason for doing it.
>
I was under the impression that SMTP negotation (just the HELO, FROM,
and TO) could take longer than the actual data xfer. If thats the case, it
seems i could be underutilizeing each box w/100 mbps nic. So I figured if
I had 4 internal ips per machine, tcp server could mux the request and
route it to the appropriate qmail-smtp. From, there I would than need
multiple queues. Still a bad idea?
> Btw. routing by email address is hard. You can't tell it's to hotmail until
> you've accepted the connection and you cannot tell hotmail which MX to use
> (leastwise not easily, a smart DNS could answer to hotmail differently from
> other sites, but that's another story).
>
Yeah, Im not going to worry about this for now.
> > For now the user directories will be over nfs, but that can be upgraded
> > later as well. There will be seperate machines for dealing with access to
> > the nfs server (for user interaction) but ultimately, outbound mail will
> > be move through qmail aswell. Authentication of users is handles on this
> > side aswell (with in house work).
> >
> > Is my thinking wrong? I am curious as to how to construct the multiple
> > queue boxes, and to see who else has has success/problems with it.
>
> This is a very common scenario you describe. Mostly ISPs hit it first,
> but large corps also have the same issues.
>
> In general, you'll want to separate out the inbound SMTP from the outbound SMTP,
> so that resources can be reserved for your sending customers.
>
If I have a seperate box for outbound messages, what are best
optimizations?
> You'll want some sort of common file store for the mailboxes (I use that word
> in the general sense, not for V7 vs Maildir distinction), making that truly
> redundant is hard so people tend to opt for high-av solutions like Netapps.
>
I was thinking along the same lines, for down the road. I assume
upgradeing to fiber or pure scsi will happen as my company utilzes this
more.
Im not sure if there is one, but a doc on large scale qmail design
questions and answers would be helpful.
Thanx for the help, BTW...
jeff...
