Debian – S.M.A.R.T Status of ServeRAID M5015 on Lenny

I can't see any reason why you wouldn't use Debian on that hardware. Even if you had to use a RedHat-patched kernel, it's still less hassle to build a customised kernel for Debian than to use a whole distribution environment you're less familiar with, but as you say, there seems to be good support for that RAID card in the Debian kernel anyway.

You need to read the release notes before upgrading to a new version of Debian. If you just blindly upgraded without reading the release notes an following the instructions you may have broken your system.

This is the quick version from the IRC help channel.

Remove volatile & backports from /etc/apt/sources.list changing lenny to squeeze.

Use apt-get for the upgrade: apt-get update && apt-get upgrade && apt-get install linux-image-$(uname -r|sed 's,[^-]*-[^-]*-,,') udev.

Install firmware-linux-nonfree if needed; check you have a 2.6.32 kernel installed aptitude search '~nlinux-image~i' and reboot into it. apt-get dist-upgrade.

If you did not preform those steps in that order you may end up with a broken system due to the kernel and udev needing to be upgraded first.