back to article Ugh, stupid power supplies hogging server density, who needs 'em?

Supermicro has added battery backup power to its disaggregated rack-scale server product line to improve power efficiency and server density ratings. Its disaggregated server architecture means CPU, memory, IO, storage and power/cooling elements can be upgraded independently. Each component can be refreshed separately to …

  1. jms222

    Commodity ness is the problem

    If servers weren't built from commodity hardware there would be more than a few percent of power savings to be made.

    For example feed in a few hundred volts d.c. and you can

    * throw away the rectfier (which you'd still need somewhere of course for mains input but can be done better)

    * have smaller input capacitors

    * throw away the power factor correction section

    * feed straight from a simplified inverter from solar P.V. or wind generator it being easier to output d.c. than synchronised 50Hz. The inverter now doesn't need those big capacitors either.

    1. Anonymous Coward
      Anonymous Coward

      Re: Commodity ness is the problem

      The problem is that even "DC" supplies have a lot of AC stuff happening. Your several hundred DC supply input will need several switch mode power supply step downs, each of which will need decoupling.

      I do agree that staying with DC all the way versus continually switching between AC and DC will have advantages. Look at what the telco guys figured out years ago with -48VDC.

      1. Stoneshop Silver badge

        Re: Commodity ness is the problem

        The problem is that even "DC" supplies have a lot of AC stuff happening. Your several hundred DC supply input will need several switch mode power supply step downs, each of which will need decoupling.

        That won't change from what is needed now; it's the power input side that'll be much simpler (rectifier and PFC can be left out).

    2. Sandtitz Silver badge

      Re: Commodity ness is the problem

      For example feed in a few hundred volts d.c. and you can

      Most servers can be powered by either telco 48V or more hefty 380VDC power delivery. Bit surprisingly Supermicro doesn't seem to offer 380VDC but (at least) HP, Dell, Cisco do.

      What you are proposing is nothing new. In ideal world every DC would be running on DC juice.

      1. Steve Aubrey
        Joke

        Same/same

        >>"What you are proposing is nothing new. In ideal world every DC would be running on DC juice."

        Well obviously. Oranges drink orange juice, right?

    3. Aitor 1 Silver badge

      Re: Commodity ness is the problem

      I agree, and then simple and efficient step down converters would suffice.

      I have seen in some old datacentres that arrangement, I just dont remeber the machines that used that.

      Also old Sun systems used 48v power supplies, etc.

      There is an interesting article on step down converters here:

      http://www.electronicdesign.com/power/aee-boosts-efficiency-lower-output-voltage-step-down-converters

    4. Stoneshop Silver badge
      Boffin

      Re: Commodity ness is the problem

      For example feed in a few hundred volts d.c. and you can

      * throw away the rectfier (which you'd still need somewhere of course for mains input but can be done better)

      * have smaller input capacitors

      * throw away the power factor correction section

      * feed straight from a simplified inverter from solar P.V. or wind generator

      * The output side of the UPS can (theoretically) be as simple as a diode between a battery of the appropriate voltage and the load. And with the generators feeding the battery charging circuitry, there's no need for them to be able to sync with the AC buses.

      Any equipment still needing real AC can take their supply from an appropriately-sized inverter per (group of) rack(s).

      There's a few caveats with distributing DC, especially at voltages over 48V, but those are solvable.

  2. Aitor 1 Silver badge

    Doubts

    I had my doubts, but the math seems legit.. it is a good idea and that number sold also means that they are easy to manage in big numbers.

    Long live to Supermicro then, they seem to be able to beat ODMs.

  3. jms222

    -48V is to do with corrosion and being a round but small number of common lead acid batteries and not quite painful to handle unless you are very wet.

    We produce a lot of our kit with -48V power supplies for data centres.

    I was amused to see the LED on stick units at every seat at the London 2012 main stadium were marked as -48V.

    Transistors for tens of volts are relatively common and cheap. Go up to hundreds of volts and it isn't so.

    The problem in the modern data centre context is the massive current required compared to running at mains voltages.

    Almost all modern switchers will work perfectly well at 80-400 a.c. or d.c. Something to think about when the grid fails and you have solar P.V. Needs a bit of jiggery pokery if the open circuit voltage is near 600v as it is with mine.

    1. J. Cook Silver badge
      Boffin

      RE: -48V...

      I can tell you that having the ground lug brush against the live lug produces pretty blue sparks. :D (Yeah, I should have wrapped that lug with electrical tape prior. I was stupid back then.)

      I can also tell you that shorting the -48 plane of a PDC to the ground plane with an uninsulated nut driver is a very good way to get forcibly removed from the data center it's installed at. (Not me, but someone else- I was told that story when I asked about the 1/8" notch in the 1/4" thick copper backplane at that data center...)

  4. Bill M

    Sun-synchronous satellite data centres

    Simple: Use sun-synchronous satellite data centres. Solar cells on the sunny side, heat sinks on the dark side and use whatever DC voltage tickles your fancy.

  5. Will Godfrey Silver badge
    Meh

    Ok, but with a caveat

    High voltage DC supplies present two significant risks.

    Electric shock is much more likely to be fatal.

    A fault creating any kind of arc will do massive damage - it won't self extinguish like an AC one.

  6. jabuzz

    You could save a bunch of power if you just had the main PSU on a computer shift the mains AC to 12V DC and do DC-DC step down at point of use for everything else. A whole bunch of inefficiency results from trying to do 12V, 5V and 3.3V all at the same time in a single step down from mains. Not only that but you can't mange good regulation of all three voltages anyway. It's all about the forward voltage drop over the rectification diode's. Google where pushing for this five/six years ago but it does not seem to have gone anywhere. Quite why a PSU manufacturer does not do single stage to 12V then a bunch of DC-DC step downs in an ordinary ATX PSU form factor beats me. To be honest for a higher wattage PSU single stage to around 24V to get the galvanic isolation then everything from DC-DC step downs, given nice tight regulation of all rails would probably be even better.

    Basically computer PSU's need some rethinking because they are currently rehashed design's from 20 years ago and things have changed, namely DC-DC step downs are now insanely cheap and reliable.

    1. jms222

      "quite why a PSU manufacturer does not do single stage to 12V then a bunch of DC-DC step downs in an ordinary ATX PSU form factor beats me."

      Err that's exactly what they do though historically 5V and maybe 3.3V and a couple of negative rails too.

      Same with our stuff. There's 3.3V, 2.5V 1.8V 1.2V, 0.8V. More voltages than you can shake a stick at. They're generated close to where they are needed. These could NOT be done in the main PSU (and work properly) for various reasons.

  7. Fazal Majid

    Fire hazard

    What could possibly go wrong with a technology (lithium batteries) with a known record of spontaneous combustion being put in a large number of small, hot enclosures?

  8. Anonymous South African Coward Silver badge

    Solar PV

    Running a Mikrotik on solar here, straight 12v from the battery. Works quite well, and saves a bit of energy to boot.

    On the other hand, having 12v stepped up to 240v (inverter or ups) then down again to 12v (mikrotik wall PSU) leads to losses during the voltage up/down conversion.

    Having said that, 12v or 48v dc for a data centre sounds good - until you factor in copper. You'll need thicker cables to compensate for resistance etc at lower volts than what you would have with higher volts.

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