I think you misinterpreted what I said. I explained it more clearly below. I suggested using the same 12 nodes but putting each one as a RAID 0, which would get you more reliability and more storage for the same cost. In your current config, two dead disks possibly bricks the system -- in the config I propose, you'd need four dead disks before anyone noticed.

What I'm suggesting is that you think of the cluster more holistically, since I assume your goal is a reliable cluster, not reliable nodes. As a nice bonus you get more "free" disk space.