We have a very relatively simple set up, looking for a very simple (reliable) solution:

One Dell box with redundant power supplies running Windows 2003, plugged into two separate APC SmartUPS 1500 units (USB, no smart cards) on two separate circuits.
EDIT: The drain of the two UPS units is not even or predictable because other systems are separately attached to one or the other of them.

Solution required:
IF (UPS1 = Low) AND (UPS2 = Low) THEN: Shutdown gracefully ELSE: DO NOTHING!!

APCUPSD only allowes for one instance (and therefore one UPS) in a windows environment.
PowerChute can't do this without using APC Smart Cards which means utilizing our switch, but the switch does not have redundant power supplies, so it will only live for as long as one of the two UPS units. And no, i don't have the budget to buy two smart cards plus a switch with redundancy ;)



Your current solution seems pretty reliable to me: If the UPS you're connected to reports low power you'll shut down.

Drain across the two units should be relatively even, so when one reports low they're probably both at a point where shutting down is advisable. The situation you're not covered for is if the other (non-monitored) UPS fails completely & the monitored one can't handle the extra load its attached power supply will demand (causing an instant failure or circuit trip). My guess is that's not very likely unless your server is really beefy.

  • 1
    true, but i forgot to mention: other systems plugged into the UPS units cause an uneven drain. i will edit the question accordingly. i guess the setup is not "simple" after all. – Make it useful Keep it simple May 28 '10 at 21:15
  • Ahh - that complicates matters, though not terribly (pick the one with the highest load as your shutdown controller). It does mean you may shut down a little sooner than you need to, but during a long-duration power failure an early shutdown is always better than [CLUNK... hey, why is it dark in here?] – voretaq7 May 28 '10 at 21:18
  • practical solution that i could definitely use, but isn't there/shouldn't there be a solution that does not rely on me/my replacement remembering/knowing to plug less systems into the monitored unit?? – Make it useful Keep it simple May 28 '10 at 21:21

You mention that these two UPSes are connected to two separate circuits. Are these two circuits connected to the same power panel (and therefore connected to the same upstream power source) or are they connected to two separate power panels each backed by a different generator?

If they are not connected to two separate generators then you might be complicating matters by adding two UPSes. At large scale, having two separate UPS systems is lost if they are both backed by the same generator. If they aren't backed by a generator at all, you might just be adding complexity instead of availability.

If power is lost and it's just a matter of time before you need to shutdown, do the shutdown. If this is really a mission critical application there will be a budget for keeping the system online (via an associated cost for the downtime, aka insurace.) When that happens invest in a very good data center space.

If you are just trying to maximize your runtime, connect your server to both UPSes and everything else to just one. Setup the the server power supplies to prefer your dedicated UPS and only shutdown when the shared UPS is low. You should be able to setup the power supply preference either in the BIOS or via the DRAC/IPMI. This assumes that the server draws more than all of the other equipment combined (which is probably a fair assumption..?) then again, we're now getting into power math which is it's own beast.


Run a small linux version virtualized on the box. Install NUT (Network UPS Tool) which will do exactly what you want. The client has been ported to Windows, but I don't believe the server has.

  • if you mean running a full virtual linux install, my server is already handling more than it should. if you mean something else, can you elaborate (or point to a link)? thanks – Make it useful Keep it simple May 28 '10 at 20:41

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