# mdadm --assemble /dev/md0 /dev/sdb1 /dev/sdc1 /dev/sdd1
mdadm: /dev/sdb1 is busy - skipping
mdadm: /dev/sdc1 is busy - skipping
mdadm: /dev/sdd1 is busy - skipping

# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4]  [raid10]
md127 : inactive sdb1[3] (S) sdd1[1] (S) sdc1[0] (S)
     5860535808 blocks

unused devices: <none>