That all I can do - bot how to get a console using a Sabayon install medium? http://wiki.gentoo.org/wiki/Dual-boot_G ... tware_raid
>You don't want to install gentoo from scratch, so you make one of the USB Disk bootable. Have a look at GRUB to get an idea. Now you boot the usb disk, mount your gentoo on /mnt/gentoo and make a system backup with
tar -c [a-k]* lib* [m-z]* |gzip -9 > /mnt/part3/gentoo.tar.gz
The term [a-k]* lib* [m-z]* is used to exclude lost+found. You have everyhting you need to setup the box again.
If you want to give dmraid a try, which has support for bios powered software raid, then you should zero out the disks with
dd if=/dev/zero of=/dev/sda bs=4k
dd if=/dev/zero of=/dev/sdb bs=4k
dd if=/dev/zero of=/dev/sdc bs=4k