As with this bug in the 2.6.5 kernel, its also, unfortunately, present in the 2.6.6 kernel, and all of the mm patches to 2.6.6. When presented with even moderate I/O on a PDC20265 controller, with one or more drives, the kernel with freak out and attempt to reset the IDE controller, which esstentially causes the box to become totally unusable. This absolutely does not exist in 2.4. The exact some hardware with any manner of 2.4 kernel, with any distributions (redhat, fedora core 1, suse, slackware and gentoo) all function perfectly, but any 2.6 based distro (suse, fedora core2 or an upgrade to 2.6 for a non-2.6 distro, like redhat 9) causes this is critical bug.

In short, if you are using a Promise controller (and at least a few highend laptops come with these now to provide RAID support), 2.6 will not work for you.