PowerEdge 2900: REDUNDANT POWER SUPPLY connection?

Or go old school?  4 to the UPS and 4 to the wall.   That is how we used to do it back in the day.

correct, 4 to one ups, 4 to another ups, and each ups should be on its own electrical grid/breaker. redundancy is the name of the game here. the two UPS should not be on the same circuit breaker andif possible, the UPS should be on completely different electrical power sources in your building, so if one goes, the other will stay up. same for  your switches etc. Its really a matter of how critical it is for your systems and switches/network to stay up.

ItalP,

The best practice isn't to have the power supplies going to individual UPS's. Best practice is to have them running to the same UPS, but to have the UPS connected to separate circuits. You can have them split to 2 different UPS's it adds another level of redundancy.

First of all, thank you everybody for the replies.

Is it possible to connect the power supplies to different models of UPS? I mean, 4 to the APC RT3000 and 4 to a APC SMT2200I? Or it's better to use the same model?

Using 2 different models or 2 identical models of different production dates (at least a few months apart) makes it less likely that a problem with the design/firmware or the battery ages causes downtime on both UPSes at the same time.

be sure to test the configuration to see how long it takes for the UPS to pickup the load in case of a power loss. There are cases where some system power supplies dont like the power coming from a UPS because of the wave form and amplitude that the UPS is putting out when a power outage occurs. Some UPS have enough of a delay to actually provide power to the system, that the power supply thinks it lost power.