mdadm --create: RUN_ARRAY failed: Invalid argument

Question

I'm trying to set up a RAID1 array, like this:

djc@miles dev $ sudo mdadm -v --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb1 /dev/sdc1
mdadm: Defaulting to version 1.2 metadata
mdadm: RUN_ARRAY failed: Invalid argument

This is with two brand new hard disks and brand new (type 83) partitions (both have a single partition). What could be going wrong here? Google is not offering much help, and I don't really understand the error message here.

Answer 1

I figured it out: my kernel doesn't contain support for RAID1. Should have enabled the CONFIG_MD_RAID1 option.