Dell (and LSI) retracted support for the 466 Megaraid SCSI RAID card driver (megaraid2) in the current Redhat kernels. As I use Redhat-derived CentOS for my production servers this is a royal pain.
I could have remained on Fedora since FC4 retains the non-mbox driver for the older cards, but the constant torrent of package updates forced me onto RHEL4 (or rather, the binary-compatible & non-supported Centos clone).
Luckily, I am not the only one in this pickle, and this site explains how to rebuild the initrd.img with the right megaraid driver. CentOS specific instructutions were posted in this article.
I have two production servers with these cards, and as a result have to rebuild the old megaraid.ko module every time a new kernel is released. In reality I simply block kernel updates in the yum config files, but that isn’t a good long-term strategy.
The following sites contained useful info: