Mark Hahn wrote: >> http://www.eweek.com/article2/0,1759,2000867,00.asp >> >> 20% is a lot, both in terms of consumption and cooling capacity. I'm > > the article says "up to 15%" at the facility level - did you get 20% > by figuring a savings at the rack level, too? I got 20% by misquoting, sorry. Still, 15% is nothing to sneeze at.
> afaikt, the article is based on an assumption that everything is powered > by an online UPS, and probably that node PSU's are low-performance (say, > 65%). sometimes studies like this ignore fact that incoming power is > inherently AC (that is, only start looking at efficiency given DC supply.) > > I'd love to see DC gain more traction - PSU's are certainly one of the > flakier components in our systems, though per node (HP DL145G2), they > only contain 2 of 14 fans (or of 18 moving parts). I don't know whether > there's a reason to think many small AC-DC PSU's would be less efficient > than a couple really big ones (factoring in the cost and inefficiency of > DC power distribution). Do your PDUs receive 220 VAC or ~400 VAC? They're talking about a 380 VDC distribution grid. On it's face, this infrastructure would be at least as efficient as a supply of 270 VAC. Unfortunately, the article doesn't lean too heavily on hard facts wrt their claims. I really just have a physicist's understanding of the forces at work here. At this point, perhaps we should get Jim Lux to educate us? > I'd certainly be interested in a distribution system (whether AC or DC) > that avoided so damn many plugs and sockets and breakers and PDUs. > I guess I'm more enthused about servers becoming lower-powered, and also > quite interested in better ways to dissipate the heat than raised floors > and traditional chillers... Heh heh. Water cooled racks? >> curious how long it would take before DC supplied racks become cost >> effective. > > well, there's already a standard DC supply - to the motherboard. > one impediment might be that it's got +12, -12, 5, 3.3 and probably > a couple others. if it were just a matter of providing lightly > regulated 12V, life would probably be a lot simpler. and I'm not sure > MB's would be much more complicated, either, since the current > main consumer, the CPU, already has a fairly flexible and high-power > onboard dc-dc converter. (I wonder how efficient it is, typically...) Well, a DC-DC power converter is pretty straight forward. I expect part of the trouble with switching power supplies is those high frequency mosfets, which you wouldn't have (I expect) with a DC-DC converter. -- Geoffrey D. Jacobs Go to the Chinese Restaurant, Order the Special _______________________________________________ Beowulf mailing list, [email protected] To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
