Recommendation for Fedora server?

Kam Leo kam.leo at gmail.com
Mon Oct 1 19:20:49 UTC 2007


On 10/1/07, Karl Larsen <k5di at zianet.com> wrote:
> Kam Leo wrote:
> > On 10/1/07, Karl Larsen <k5di at zianet.com> wrote:
> >
> >> Bob Goodwin wrote:
> >>
> >>> Les wrote:
> >>>
> >>>> These supplies are switching supplies, not linear.  You should check
> >>>> some of the draws, I think you will be surprised about how little some
> >>>> of them draw (admittedly there are various design strengths out there.)
> >>>>
> >>>> In general, a linear supply is about 20-35% efficient, meaning that a
> >>>> 450 watt supply would draw about 90 watts all the time.  But these new
> >>>> switchers are about double that or more, meaning that the supply will
> >>>> draw somewhere between 20 and 50 watts.  Moreover that draw will
> >>>> basically be independent of the size of the ultimate supply, simply
> >>>> existing to control the switcher itself, and not the drive current.
> >>>> Technology exists in some forms of "buck control" that could boost the
> >>>> on line efficiency further reducing the drain.  Power stuff is evolving
> >>>> even faster than much of the other technology, but is less glamorous, so
> >>>> doesn't get as much of the press.
> >>>>
> >>>> Regards,
> >>>> Les H
> >>>>
> >>>>
> >>>>
> >>> Here's some more interesting information on power supplies.  Note that
> >>> best efficiency is attained at/near maximum load.  So a 500 watt
> >>> supply looks good but may not be what you want when considering power
> >>> consumption and disposing of waste heat.
> >>>
> >>> http://services.google.com/blog_resources/PSU_white_paper.pdf
> >>>
> >>> Bob Goodwin
> >>>
> >>>
> >>     Hi Bob, I am interested in what Google has done but need a lot more
> >> information. They say changing the PS to one making just plus 12 volts
> >> will save energy. I do not see that as a given. In fact it makes me
> >> think they are just passing on the voltage change to the mother-board
> >> makers. I think the idea being the MB makers can make just the other
> >> voltages their board needs. But converting 12 to 1.5 volts with economy
> >> of power is complex and will jack up the MB cost somewhat, and will make
> >> it hotter.
> >>
> >>
> >>
> >> --
> >>
> >>         Karl F. Larsen, AKA K5DI
> >>         Linux User
> >>         #450462   http://counter.li.org.
> >>
> >
> > They're trying to get rid of distributing AC to all the racks and the
> > losses resulting converting from AC to DC for each MB.  If the MB
> > design only requires 12 VDC input then it is more efficient to have
> > only one AC to DC converter and buss the DC to all the boxes in a
> > rack. By the way, people have been bussing 24 and 48 VDC in equipment
> > racks for years.
> >
> >
>     The 12 volts can not be moved as 12 volts DC very far. The length of
> a car is about it. So Google must have a lot of racks in close proximity.
>

It's probably more like one AC/DC converter per rack. Similar to a
blade system where there is one power supply sending regulated power
to blades which plug into the main chassis.




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