Recent versions of `mdadm` stopped accepting `/dev/disk/by-id` symlinks
as the MD device:
> mdadm: Value "/dev/disk/by-id/md-name-backup5" cannot be set as devname. Reason: Cannot be started from '/' or '<'.
To work around this, we need a script to resolve the symlink and pass
the real block device name.
This udev rule will automatically re-add disks to the RAID array when
they are connected. `mdadm --udev-rules` is supposed to be able to
generate such a rule based on the `POLICY` definitions in
`/etc/mdadm.conf`, but I was not able to get that to work; it always
printed an empty rule file, no matter what I put in `mdadm.conf`.
The `raid-array.yml` playbook can create Linux *md* software RAID arrays
using the `mdadm` command. Two variables are required: `md_name` and
`raid_disks`. The former is a string name for the array. The latter is
an array of paths of block devices to add to the array.
