What are the setting options in UPS for controlling that function?
I'd be sure to have the UPS power auto shut-off set with a reserve
of at least 25%, especially if you choose auto-start, so there may
be some time for the battery to recharge, or so the unit may be able
to protect the Mac should another outage occur shortly after the first.
Depending on how you use your computer, and the capacity of the UPS
(duration of runtime on battery power) your settings will vary. As my Mac
has an APC UPS unit of limited power reserve, I am sure to not let it sit
there & waste the battery until near zero, because recharge takes hours.
Are you using the Mini Server, as a Server? (One of mine is a Server, &
the same vintage as yours, but not in-use as such, at the present time.)
With mine, since I don't want to have them on and off again if I am not
there to be sure things are correct (poor power grid here, and no means
of communicating an outage to the provider, since all phones die, too)
my settings are quite different where I am now, in a city that is backward.
Mine is set to shut off and not auto-start on resumption of grid power.
Across both possible choices of these settings, be sure there is a
continuity so at least until you can be there and test it yourself, it
would not be restart. Not unless there is adequate power reserves.
You could test the UPS (as I've had to do, after finding a new unit that
was fully charged, fail and crash my Mac) by putting a load on it, then
pull the AC power to the UPS, so it reacts like the power went out. To
see if I could kill my UPS (without mac attached) I repeatedly put the
power to the UPS and removed power, for quite some time. This, after
the unit failed under load, with a full 24 hour charge, in first-use, new.
My choice was to put a 1,000watt halogen light on the UPS, to try &
make the switching circuit permanently fail under warranty, so I could
drive it back to town (120 miles) and get another. It didn't fail, though...
My older Mini has the UPS control over power to both Mini Macs; it is
set to shut down at 30% power, and when I am not going to be in the
area (out of town a day or two) I shut down my computers since I am
in the present company of idiot urbanites whose power grid is worse
than what I'd been accustomed to in a somewhat rural AK location.
Not being able to report outages or call 9-1-1 is an urban mystery here.😐