Comment # 1 on bug 1187656 from Coly Li

(In reply to Daniel Molkentin from comment #0)
> The /usr/lib/systemd/system/mdcheck_start.service file states the following:
> 
> [Service]
> Type=oneshot
> Environment="MDADM_CHECK_DURATION=6 hours"
> 
> "oneshot" implies that the service will remain in "activating" state for the
> entire duration (long, up to the stated 6 hours.
> 
> It would be better to use Type=simple, which does not keep the unit in
> "activating" mode. This is an important difference in semantics, because
> monitoring tools (e.g. prometheus) tend to alert if a unit is stuck in
> "activating" for more than (typically) 5 minutes (which usually makes
> sense, but not here).
> 
> The only side effect that I could find is that systemd will not wait for
> follow-up units to start, but since this is a timer-triggered unit,
> I would not expect anyone else to depend on this service.
> 
> Verified by adding an override file.

IMHO the above opinion makes sense. Let me try to post a change to upstream and
see whether mdadm maintainer likes it or not.

Thanks.

Coly Li