In $PREVIOUSJOB, we had a number of internet facing SMTP machines, which looked up accounts/mailboxes/transport maps etc from MySQL; all changes were done on a master database on a separate machine, and synced out with MySQL replication to all of the SMTP machines. This way we could take any single machine offline, be it an SMTP server or the master database, and nothing would break.
Load balancing was done by a pair of atom-based machines running Linux and Keepalived. I'm not sure the Atoms would have scaled well past 100M of traffic, but if you have more than 100M of SMTP traffic coming in you can likely put in whatever you like for load balancers. The whole setup worked extremely well, almost to the point where it was boring. Just as it should be. On 14-02-07 01:10 PM, Len Conrad wrote: >> I have an email receiving setup with one Postfix instance mapped to one >> instance of Amavisd-new (spamassassin, ClamAV), >> >> Now to prepare for increasing traffic, I am looking on to scale out >> strategies of my setup. >> >> So with that in mind, is it possible that one instance of Postfix can itself >> distribute email load on two or more Amavisd-new instances spread over >> different locations over the network >> ? >> >> In essence can postfix work as an SMTP load balancer ? > not load balancer, but (dumb) load distributor via DNS round-robin. > > My envelope-only-filter mx1 relays to cs.mydomain.net, a domain record set > which has 3 IPs, one for each of our content-scanner boxes. > > I shown several times that DNS round-robin on an internal network like above > sends splits the load to target IP +/- 2%. > > For intelligent load balancing, you could have a looping script that > SMTP-connects to each IP in the target record set every minute, to remove a > slow-responding IP from the record set with nsupdate, or to add an IP that > returns to quick SMTP responding. > > Above, cs.mydomain.net would have to be defined as a dynamic zone with > allow-update from the IP running the monitor script. > > Len > > > > > -- Looking for (employment|contract) work in the Internet industry, preferably working remotely. Building / Supporting the net since 2400 baud was the hot thing. Ask for a resume! ispbuil...@gmail.com
