I'm running Debian Lenny (Stable) on my server and was upgrading the disks (from 250G IDE to 1T SATA). While I was at it, I thought I'd improve the partitioning too. The old disks have each RAID array on a separate partition but that isn't necessary on recent distributions (Ubuntu Lucid, Debian Squeeze, etc.).

I thought I try creating just two arrays and partitioning the arrays rather than the underlying disks. If nothing else, it makes resizing them substantially easier.

I created my two arrays (the first for /boot and the second for everything else) and partitioned the second array for / and /home. However I can't seem to get mkfs to format the partitions. It doesn't recognize /dev/md0p1, for example.

Does anyone know if this a problem with mkfs or with the 2.6.26 kernel? Could I format the partitions using a live CD and access them or is the 2.6.26 kernel incapable of recognizing partition tables in raid arrays?

To answer my question, I booted from an Ubuntu CD and formatted the partitions on my RAID array. However Debian/Lenny still wouldn't recognize them.

Next I took a Debian/Squeeze netinst CD and tried to install it on the / partition. No luck. The installer only shows the RAID arrays, not the partitions on them.

Since I can do this with Ubuntu but not Debian despite Debian/Squeeze having the more recent kernel and mdadm version, I'm not sure what's going on. It's probably an installer limitation.

Next step I guess is to do a full-upgrade of my server to Debian/Squeeze and copy to the new RAID array (assuming that it is recognized properly). The other option would be to install Ubuntu sever but I think for now I'll stick with Debian.

I finally got this to work by installing Debian/Squeeze to my old / RAID array. Once installed, it was able to recognize the partitions on the new RAID array. I mounted them and rsync'd the old RAID arrays to the new partitions. After that, I installed grub on the new disks and was able to boot into the new RAID array.

It seems to be a limitation/bug of the current Debian installer that it can't handle partitions in RAID arrays. The older 2.6.26 kernel doesn't seem to be able to either.