The mdadm tool is still missing on the latest live cd though the 2.6 series of the linux kernel is supported now. It would make handling md-soft-raids easier because you do not have to create da raidtab each time you reboot. BTW: greetings from LinuxTag :) Reproducible: Always Steps to Reproduce: 1. 2. 3.
Try the experimental CD in the /experimental/x86/livecd folder on your local Gentoo mirror. We added this to the catalyst templates a while back, so it should be on every new LiveCD we create.