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Facebook Putting Batteries On-Board Its Servers 155

Posted by kdawson
from the following-where-the-big-boys-lead dept.
1sockchuck writes "The data center of the future may have no central UPS units, and be filled with servers with on-board batteries. Facebook says it will adopt a new power distribution design that shifts the UPS and battery backup functions from the data center into the cabinet by adding a 12-volt battery to each server power supply, an approach pioneered by Google. Facebook says the move will slash its power bill and save millions in capital expenses on UPS systems and PDUs. Facebook acknowledged that these types of custom designs are limited to large companies, but called on server vendors and data center builders to adapt their offerings to make them available to smaller companies."
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Facebook Putting Batteries On-Board Its Servers

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  • Re:12 Volt? (Score:5, Informative)

    by TheKidWho (705796) on Friday November 27, 2009 @02:09PM (#30247188)

    Since when is 12 Volts a measure of battery life? You still need to know how many Amp-Hours the battery can provide and the power usage of the server.

    You could have a 100Amp-Hour 12 volt battery, or a 1Amp-Hour 12 volt battery...

  • units (Score:3, Informative)

    by SuperBanana (662181) on Friday November 27, 2009 @02:39PM (#30247464)

    How long is twelve volts going to keep a server running? A UPS would guarantee that you have enough time to finish transfers and close connections before shutting down into a safe mode, even give clients a warning before shutting down.

    Volts are a measure of electrical potential, not capacity. You mean watt-hours, most likely.

    How long is twelve volts going to keep a server running? A UPS would guarantee that you have enough time to finish transfers and close connections before shutting down into a safe mode, even give clients a warning before shutting down.

    That depends on how big the UPS is. Many large-scale datacenter UPS's are only designed to ride out the time between when the power goes out and the generator is warmed up enough to take the load (tolerances are not 'right' when the engine is cold, so damage is caused, or the engine won't provide rated output.)

    The argument is that in a "cloud", none of this matters- you only need to ride out a temporary power outage, or allow the machine to shut down properly so it doesn't have to be repaired software-wise. However, for the rest of us who don't live in poofy clouds and have non-cloud things like mail servers, yeah, you're right- the capacity in a server is pretty low.

  • by Cassini2 (956052) on Friday November 27, 2009 @02:41PM (#30247486)

    277 (V) corresponds to the line to neutral voltage of a 480 (V), 4 wire power distribution system. 480 (V) systems are fairly common in industrial settings in the United States. The major disadvantage of using 480 (V) to power a server, is you can't use a UPS. UPS on 480 (V) systems are rare and expensive, hence the reason why Facebook wants the batteries inside the server.

    I'm pretty certain you really don't want to run servers from the 277 (V) line to neutral voltage of a 480 (V), 4 wire system (3 lives, one neutral). On a 4 wire system, you have 4 wires and you can lose any one of them. If you lose the neutral, your servers could be running of 480 (V) instead of 277 (V). They will be destroyed.

    Losing the neutral is a relatively common failure in 3 phase systems, as many 3 phase systems are 3 phase, 3 wire with a fake neutral/ground connection that is often mistaken for a neutral. This central connection is purely to prevent the 3-wire system from drifting off of off ground, like when lightening strikes, which is common in a big high-voltage system. When operating a 10,000 (V) to 480 (V) step down transformer (the transformers inside the metal fenced enclosures), a small amount of electric slippage to occur between the windings. 1% of 10,000 (V) is 100 (V). Faults can also occur in big loads, like motors. A 10% ground fault on a 480 (V) 400 (A) motor, could be 200 (V) at 40 (A). These voltages/powers are nothing for a 480 (V) motor, but are enough to cause significant damage in a computer with a 1.2 (V) processor. This mismatch is why you should never trust the ground/neutral connection on a high-voltage supply line. It is for safety, not for powering computer equipment, electronic equipment, and electronic motor drives. After having replaced tens of thousands of dollars of electronic motor drives, my rule is: make the supply 480 (V) 4 wire, and all the loads 480 (V) 3 wire. A 3 wire load with no neutral can withstand problems with the neutral. A 4-wire load powering electronics line-to-neutral will not withstand neutral failures.

    If you are going to use 480 (V), you really want to use 480 (V) 3 wire AC (3 live wires, no neutral). If any one power circuit is lost, nothing really bad happens. Also, power semiconductors are readily available for 480 (V), because all the industrial motor drives require them. As such, your power supply will be cheaper.

  • Re:12 Volt? (Score:3, Informative)

    by PIBM (588930) on Friday November 27, 2009 @02:42PM (#30247496) Homepage

    Small personnal UPS usually gets 2 12V battery at 8AH to 12AH. In a server environment using the google way (cheap quad core), the computers are probably using under 200W (no video card) and probably around 100W avg. (no hard drives everything by lan?). a 12V 8AH battery can provide 96W for an hour, less the convertion rate, so it`s more than is required to put the generators online.

  • by mhollis (727905) on Friday November 27, 2009 @02:45PM (#30247542) Journal

    I used to work at a company that decided to install large, monolithic UPS systems after the power company hit them with a spike that took the entire system down for over a half hour. As they're a broadcasting company, they (rightly) felt that feeding their network affiliates nothing was not a good idea.

    As a result, they have these UPS "rooms" that hum like the dickens when you're passing them in the hall, all with batteries that will need to be replaced regularly (just like the Google server battery systems, so it's the same problem no matter what). Reason for the hum?

    The hum is caused by these giant transformers that step the power from DC to AC and create 110 volts of AC current at whatever amperage is required for normal devices. But there is a lot of wasted energy in doing that.

    Computers and servers all run off of DC power. They plug into AC power and then run that AC through a "power supply" that converts that to DC that the computer can use. That takes power, but power is plentiful when it comes from the power company and you pay your bill on time. But when you take the power from the power company, then change it to DC to charge batteries and then take power from those batteries to change it to AC to power normal wall outlets only to take that through a server's power supply to change it to DC again for the computer to use it, you're looking at lots of wasted energy in just changing from AC to DC, back and then back again, as well as changing to the kind of voltage and amperage needed to run the microprocessor, power the memory and power the drive arrays.

    So this is all about lowering consumption. And if you lower consumption, you lower your electricity costs.

    The hobbyist magazines were all aflutter some years ago about using photovoltaic (solar) energy to power a house. But what everyone had to do (early on) was to change their appliances (or order special ones) to run on DC -- not because you couldn't make AC current from the DC output of the photovoltaic systems but because it took a lot of energy to do that and these hobbyists were all about trying to save so much energy that they could take themselves off the grid.

    Here, on a large scale, you see the same idea. It's just more efficient to do this. And one of the big arguments in the early years of electrification was between DC power distribution (Thomas Edison) and AC power distribution (George Westinghouse and Nikola Tesla). We may wind up fighting these battles again in the near future.

  • by girlintraining (1395911) on Friday November 27, 2009 @02:57PM (#30247670)

    Or why not use DC for the entire data center and put the battery at the Data Center level?

    12VDC, each unit needs 300W at least... That's 25 amps per unit. Think wire gauge [windsun.com]. That's the reason, long and short. That, and you can't run 12VDC very far before power loss becomes a significant consideration.

    Tesla figured this out over a hundred years ago -- AC powers and transformers = more efficient.

  • by ThreeGigs (239452) on Friday November 27, 2009 @03:02PM (#30247726)

    Another idea behind a UPS is _a_single_point_of_failure_. Moving the power backups to the individual servers eliminates that worry. Plus, since the servers are already redundant, you don't need the redundancy on the UPS, inverters, etc., which should save money.
    And since it's long-term, I'm willing to wager it won't be lead-acid, but NiMH. So no real maintenance issues. And your "what happens if..." scenarios apply equally to a battery in a megawatt UPS or a battery in a server.
    As for battery management and 'specialized' power supplies, etc.: go check out a laptop. That wheel has already been invented, and better yet, has benefitted from mass-production.

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