Talk:Home Server

It is said that the OS should be on /dev/sda being a small drive, the rest being in RAID 5.

I would definitely put RAID1/5 on the OS too, since you do not want to reinstall again a Gentoo Box, in case of a disk failure. A reinstalation would cost at least few hours. Then setting up the box will take much longer. Furthermore, having SWAP on RAID is also advisable.