We've just transfered our moodle installation to a small prototype high-availability cluster. We're hoping to convert this to be our production server soon and I'm wondering if anyone else has run moodle on a cluster and has any advice? I've scanned through the archives and found a little but not much detail. Are there gotchas we should be aware of before making this server production?
Our configuration is based upon: http://www.linux-ha.org/ We have two machines acting as directors with a heartbeat between them so that if one goes down, the other takes over. Behind them are currently just two servers. Each is running apache and the directors do load balancing between the two servers. The data is shared, stored on an external NAS device. (The NAS has RAID with a hot spare, so hopefully this isn't too much of a weak point; in principle the NAS also support data replication through it's firmware with another redundant device) We have one of the internal servers running mysql with a second heartbeat setup between them so that one can take over if the other goes down. We had some trouble initially getting mysql working smoothly, but now the system seems stable.