[rbanffy]

I don't get the AC PSUs on the servers (http://opencompute.org/servers/). Any reason why those are being used when each 6-rack group has a UPS (and batteries) connected to them? Going DC would get rid of the inverter on the UPS out and the 200 or so PSUs on each server.

[daveman692]

Amir Michael who worked on the hardware team said, "The utility provides us with AC voltage which we then convert to DC very close to the motherboard in the power supply. Our goal was to bring the high voltage as close as possible to the load to minimize IR losses. We could do an efficient AC –DC conversion in the rack and then distribute DC to the individual servers but that would mean several feet of low voltage conductors which would be made from large copper bars and a would have higher IR losses."

[lrcg]

The UPS doesn't need an inverter - the PSUs have a DC in.

[rbanffy]

But they are supposed to use the AC input when not running off the UPS. I wonder why that would be a good idea.

[dhess]

I'm also puzzled why they don't go all-DC. This thread doesn't appear to be getting any traction here. Is there a HN for datacenter geeks?