Currently the mdraid init script will always assemble and run an array, even if it's in degraded state. In case of bad cabling or some other reason causing a perfectly fine disk to not show up this results in a degraded array which might require to go through a rebuild once it's added back (even though mdadm --re-add MIGHT avoid it). However, mdadm has a --no-degraded switch to avoid this. It would be nice if there was either a MDADM_OPTS variable settable in /etc/conf.d/mdraid or a MDADM_NO_DEGRADED variable that could be set to use this switch..
should be all set now in the tree; thanks for the report! Commit message: Add a conf.d setting to pass options to the assemble step http://sources.gentoo.org/sys-fs/mdadm/files/mdraid.confd?r1=1.1&r2=1.2 http://sources.gentoo.org/sys-fs/mdadm/files/mdraid.rc?r1=1.6&r2=1.7
