Recommendation for Fedora server?

[Karl Larsen]

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.



-- 

	Karl F. Larsen, AKA K5DI
	Linux User
	#450462   http://counter.li.org.