sudo mdadm --stop /dev/md0
sudo mdadm --remove /dev/md0

mdadm: Unrecognised md component device - /dev/sdd

pbrink@groot:/mnt$ sudo parted /dev/sdd print
Model: ATA WDC WD20EZRX-00D (scsi)
Disk /dev/sdd: 2000GB
Sector size (logical/physical): 512B/4096B
Partition Table: msdos
Disk Flags:

Number  Start  End  Size  Type  File system  Flags

sudo mdadm --create --verbose /dev/md1 --level=5 --raid-devices=3 /dev/sdg /dev/sdh /dev/sdd

mdadm: /dev/sdd appears to be part of a raid array:
   level=raid0 devices=0 ctime=Wed Dec 31 19:00:00 1969
mdadm: partition table exists on /dev/sdd but will be lost or
   meaningless after creating array