There is a script /usr/share/initramfs-tools/scripts/local-top/md in the mdadm package.
It scans only the hda1, hda2, sda1, sdb2, etc but no the hda, hdb, sda, sdb.
There is a cycle in this script that wait 180 seconds on every boot for timeout of the scanning the possibly raid member disks to determine which raid level module need to load into the kernel.
There is a script /usr/share/ initramfs- tools/scripts/ local-top/ md in the mdadm package.
It scans only the hda1, hda2, sda1, sdb2, etc but no the hda, hdb, sda, sdb.
There is a cycle in this script that wait 180 seconds on every boot for timeout of the scanning the possibly raid member disks to determine which raid level module need to load into the kernel.