Is IBM's Big Iron also Big Green? (InfoWorld) [LWN.net]

InfoWorld reports on IBM's efforts to save power by moving 3,900 of its servers to 30 virtualized System z9 mainframes. ""The cost of energy, power to run computers, storage, and networking equipment, as well as the power to the cooling equipment, is becoming the highest single cost of managing a datacenter," says David Gelardi, VP of industry solutions at IBM. "IBM took a look at these very interesting plums coming to the forefront at the same time. We have an opportunity with systems management tools, with Linux, and with virtualization, to be able to take the workloads that are principally running on much smaller, underutilized Unix servers and move them over to those 30 very large mainframes.""

(Log in to post comments)

Is IBM's Big Iron also Big Green? (InfoWorld)

Posted Aug 6, 2007 2:46 UTC (Mon) by xoddam (subscriber, #2322) [Link]

Inter alia:

"...mainframes are designed with a central AC/DC power converter, which
operates at over 90 percent efficiency, compared with many existing rack
server power converters which operate at 70 percent..."

I've often wondered why, when all the electronic equipment in an office or
server room runs on direct current (and a multitude of step-mode
transformers convert between voltages inside them), we still ultimately
plug everything separately into an AC power supply with a different-shaped
adapter, occasionally blowing something up when we plug 115V 60Hz
equipment into a 240V 50Hz supply.

Why are 12VDC power outlets only found in cars?

Is IBM's Big Iron also Big Green? (InfoWorld)

Posted Aug 6, 2007 3:18 UTC (Mon) by dlang (✭ supporter ✭, #313) [Link]

most telephone equipment runs on 48v. and many of the PC manufactureres will sell you systems that take 48v power

one reason you don't see a lot of low-voltage equipment is that as you drop the voltage you increase the current, and the higher the current the more you loose to any resistance (be it a plug or a thin wire)

as a result it's only worth doing when you can make the central power supply significantly more efficient then the individual power supplies would be. in a large datacenter you can take advantage of the fact that many UPS systems arrange their batteries in banks of 48v, and eliminate the DC->AC conversion out of the UPS.

the other thing that will make it worthwhile is if the central power supply is significantly more efficient than the individual ones are. In the past individual PC power supplies have been horrible (in some cases down to 50%), now days they are averaging around 70% with high efficiency ones in the 80-90% range. if the high efficiency ones keep becoming more popular (they are normally quieter and cooler as well as cheaper to run) the gap will shrink

Is IBM's Big Iron also Big Green? (InfoWorld)

Posted Aug 11, 2007 19:11 UTC (Sat) by giraffedata (subscriber, #1954) [Link]

many of the PC manufacturers will sell you systems that take 48v power

I assume that's because some computer rooms have 48v power supplies, based on batteries? Because it doesn't address the question here at all -- you still have a standard voltage which has to be converted to the required voltage inside every machine. I don't think there are any components in PCs that use 48v directly.

The 12v outlet in a car isn't good enough to run computers. Its voltage varies widely (25% is a good assumption) and can't give you more than about 150 watts. It's also expensive because of the large wires needed. I've been hearing for years that cars are going to go to 24v systems, converted to 12v (or less) at each device.

Is IBM's Big Iron also Big Green? (InfoWorld)

Posted Aug 11, 2007 22:07 UTC (Sat) by dlang (✭ supporter ✭, #313) [Link]

remember that PC's use many different voltages internally

even the 12v power rail is usually not used to power 12v devices (the one common exception is motors in fans and drives) your high-end CPU that has a special 12v plug on the motherboard is converting that 12v down to the voltage the CPU actually uses (~3v), and your expensive video cards that have the 12v connectors on them are running chips that need 3 or 5 volts.

so whatever you do (short of running a whole bunch of different wires to the computer) you are going to be converting the voltage. it's just a matter of creating the most efficient conversion you can.

48v systems are common because that was the standard voltage for telco systems for many years, and so there's a lot of infrastructure and standard components in place to support it