Investigating with fdisk I discovered that after this the second disk in the array was reported to have the following issue: 'MBR/GPT mismatches'.
I managed to get things fixed and the partition table created successfully with fdisk instead. -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org