On Wed, 30 Apr 2008, Dexter Filmore wrote:

I'd like to assembla manually to investigate why the bloody 5th disk flies 
from the array at EVERY boot time (third so far, wonder how much stress the 
disks take) but I can't seen to disable it.

All 5 disks are 0xFD, but I passed raid=noautodetect to the end of the kernel 
line, I set "assemble at startup" in /etc/defaults/mdadm to "false", I 
cleared the mdadm.conf - still it assembles the array. No idea why.

you need to rebuild your initramfs after you make those changes to 
/etc/defaults/mdadm ... easiest is:

dpkg-reconfigure linux-image-`uname -r`

-dean