Adding a redundancy to Mac Mini Server using Mt. Lion

Currently we are using a mac mini with MT lion server. Everything is working great, but i want to create redundancy backup with an additional Mac mini. What is the best way to proceed? We know about target disk mode. Do we need additional Raid software? Any advice would be greatly appreciated.

"Take one Mac mini server configure as you like and enable its boot drive as a RAID member. Boot the other Mac mini server into Target Disk Mode. Connect them with a FW-800 cable (or ThunderBolt cable if the equipment supports it). Add the TDM mini to the mirror that the boot drive is in."

Is the above solution acceptable?

Thanks!