The shutdown/startup issue is 'working as designed', there's a kernel boot parameter to allow an array to start up in a degraded state. I don't agree with this, but it's easy to work around.
The long rebuild times, as far as I can make out, are normal.
As to the occasional dropouts and the mirror failing to establish itself, the latter has only happened once - nothing much in the logs. Haven't looked at increased logging for the other case.
Biting the hand that feeds IT
