Fail all the devices, then remove them, then stop the raid. eg

mdadm –manage /dev/mdfoo –fail /dev/sdfoo

mdadm –manage /dev/mdfoo –remove /dev/sdfoo

mdadm –manage –stop /dev/mdfoo

mdadm –zero-superblock /dev/mdfoo

viamdadm delete linux raid – Linux/BSD.