Upstream is aware of the issue, which occurs with version 0.90 md arrays. The latest git version fixes the problem. So it's only a matter of waiting for a new release version from upstream for this to trickle into the arch repos. For now I simply keep mdadm pinned on v3.1.5, which is in fact the version currently recommended by upstream unless you need the features introduced in 3.2.1. - Norbert
