Originally Posted by DotHQ
Are you running a DB on the servers?
If it is a database driven web site you will have to have an external db server or a external disk array with both apache servers having access to the db on the array's.
The problem being if one server fails mid transaction how do you know if the db on the other server has been updated? Even with a mirror there is delay. I've found no cheap way to accomplish this. But ....I'll admit it has been awhile since I looked into this (a year or so).
No, there really is no cheap way to do this effectively. You get what you pay for in this case.
You can come close with some manual juggling, like having a mirrored disk set, and periodically 'breaking' the mirror, removing the drive, and putting a blank/old one in to remirror to, and putting the one you just removed in a different location. But this is risky, involves downtime, and is VERY manual. Snapshots with systemimager or mondoarchive will let you recovery quickly, but your server will still be down while you do it.
The only 'real' way to do it is to have a duplicate server, either in a cluster or pre-configured in a 'hot-standby' mode, so that if one fails, the other takes over. Database driven? MySQL replication or Oracle RAC. If you want 24/7/365 with no downtime, you're going to have to have a fat wallet, the willingness to spend it, and some skills to configure it all.