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How to setup UPS for redundant power supply if 1st UPS goes down then system should work on 2nd UPS if 2nd goes down then system should work with 1st UPS like server power supply.

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You can connect a server with redundant power supplies such that each power supply is connected to a different power source (different UPS). If any power supply or UPS goes down, the other one will be available (hopefully).

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+1 - Simply put, ensure your server has dual power supplys and then attach a UPS to each of them. If you choose APC then you have more control using powerchute. – JamesK Dec 13 '10 at 9:49
+1 on that. UPS are pretty safe per se, so if you are afraid of that.... go redundant all the way. – TomTom Dec 13 '10 at 9:51
+1 for this answer - as an addition, if you can make sure each of your UPS is on a different circuit for its own power source. – Jeff Miles Dec 13 '10 at 15:58
@Jeff Miles: Yeah, it would be even better to do. – Khaled Dec 13 '10 at 18:54

If you don't have redundant power supplies in the systems, you can use an Auto Transfer Switch to automatically switch between two UPSes but provide a single power feed out of it. Having redundant power supplies is the best way to do it though.

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An ATS is a good solution for devices that where you don't have the option of having multiple independent PSUs. Its not cheap though ... – pfo Dec 13 '10 at 11:46
I guess it depends on your definition of "cheap" -- nothing on servers is "cheap" :-). To anchor the discussion: I think we pay around $450 for the APC ATSes we use, and $200 per power supply for redundant power supplies, so either way you're paying over $400... – Sean Reifschneider Dec 13 '10 at 11:59

Whatever you do, do NOT daisy-chain the UPS's together. See

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