Can I use RAID?
Yes. With both the Unslung-able firmware How to enable RAID support in Unslung-able and Debian (summary below). OpenSlug is capable of RAID support but nobody has tried it yet.
Steinar adds: I've tried RAID1 in OpenSlug 2.70 and 3.10 (on flash cards). It works fine and a raid device can even be used as the root file system. It requires the md and the raid (like raid1) kernel modules, mdadm and some simple editing in the boot files.
Raid1 is also working with DebianSlug (see http://wiki.nslu2-info.de/pmwiki.php/HowTo/DebianSlugRaid1 (German only)). The instructions are pretty much based on the Unslung Raid1 HowTo.
In order to make it work, make sure you have md and raid0,1,5 loaded into kernel.
For Debian (at least Lenny) the instructions at http://www.howtoforge.com/software-raid1-grub-boot-debian-etch(approve sites) work fine. Simply ignore the sections on Grub as update-initramfs reflashes the kernel and initramfs automatically and leave disks connected throughout the process. In summary (without details of each command):