The hard drive crash threw me offline a few days due to strange problems with software raids, Xen and acpi. Turns out that using the latest Xen kernel from debian testing branch on a software raid only works of you don’t set “acpi=off” as a kernel parameter. If acpi is turned off, the script “scripts/local-top/mdadm” in the initrd can’t find the devices needed to mount the software raid … causing the whole boot process to come to a grinding halt.
If I find some time I’ll do some more tests, untill then my server will be running with acpi turned on
btw. the hard disk replacement was easy. after the new drive was popped in it was just a copy the partition table and add the partitions of the new disk to the raid