Hi!
You have it correct, there would be two (or more) different sites for complete site failover no shared IPs etc... I.e. if City A gets a blackout, City B should still be fine.
If you access to your OTRS service via DNS, you're going to have some service downtime, because if you change the IP address where OTRS is listening to, you need to change the A record for, say, otrs.foo.bar. That implies some lag until changes are effective on the net, even with TTL=0 (think about proxys, dnscaches, browser caches, etc). But if you control from and who will be accessing to your OTRS service it can be a good solution. In a High Availability setup, you can use DRBD (www.drbd.org) to replicate your data via internet (I would use a VPN tunnel to protect my data). You're going to need some bandwidth, depending on how much information you send/receive in your system. Heartbeat can be used to start/stop all the services (Apache, Mysql, drbd) and, instead of moving a floating IP, to change the DNS entry for OTRS. You can write your own scritps for Heartbeat, so it will do what you need to do... Maybe MySQL replication is enough, but I'm not completely sure that everything that OTRS needs to run is stored in the DB. A good option is to use a multimaster DB and drbd for the rest of files. In my setup MySQL data files are kept in sync via DRBD, as if they where regular files... so good so far! There are other alternatives, this one is the first that came to my mind... I hope it helps! Regards! Víctor.
Thanks,
Trevor -- Heredocs, theredocs, everwhereadocsdocs old macdonald had a server farm he eyed the I/O
--- Victor R. Rodriguez Departamento de Sistemas Valoraciones del Mediterraneo, S.A. ---