I wrote this up a while ago and decided that I didn’t want to lose it in a shuffle of documents during my transition to a new workstation. It’s the basics of setting up Heartbeat (LVS) + DRBD (block replication between active/passive master servers) + MySQL. This should give you the basics of a H/A system without the benefits of SAN but also without the associated cost. The validity of this setup for H/A purposes is highly dependent on your workload and environment. You should know the ins and outs of your H/A solution before deciding to blame the system for not performing as expected. As with all production systems you should test, test, test and test some more before going live.
When I get around to it later I’ll post my How-To for setting up RHCS + SAN + MySQL. You can download the DRBD document PDF here: DRBD_LVS_Install-Configure_HowTo