[Beowulf] DC powered clusters? - fun

Alvin Oga alvin at Mail.Linux-Consulting.com
Sun Mar 7 03:00:56 EST 2004

hi ya andrew 

fun stuff ... :-)  good techie vitamins ;-) - lots of thinking of why 
it is the way it is vs what the real measure power consumption is

On Sat, 6 Mar 2004, Andrew Piskorski wrote:

> Some rackmount vendors now offer systems with a small DC-to-DC power
> supply for each node, with separate AC-DC rectifiers feeding power.  I
> imagine the DC is probably at 48 V rather than 12 V or whatever, but
> often they don't even seem to ay that, e.g.:
>   http://rackable.com/products/dcpower.htm

i don't like that they claim "back-to-back rackmounts" is their "patented
technology" ... geez ... 
	- anybody can mount a generic 1U in the rack .. one in the front
	and one in the back ( other side ) ... ( obviously the 1U chassis
	cannot be too deep )
> Has anyone OTHER than commercial rackmount vendors designed and built
> a cluster using such DC-to-DC power supplies?  Is there detailed info
> on such anywhere on the web?

dc-dc power supplies are made literally and figuratively by the million
various combination of voltage, current capacity and footprint

	( see the list of various power supply manufacturers )

> Anybody have any idea exactly what components those vendors are using
> for their power systems, where they can be purchased (in small
> quantities), and/or how much they cost?

you can buy any size dc-dc power supplies from $1.oo to the thousands

if you want the dc-dc power supply to have atx output capabilities,
than you have 2 or 3 choice of dc-atx output power supplies:
	- mini-box.com ( and they have a few resellers )
	- there's a power supply company that also did a variation
	of mini-box.com's design ... i cant find the orig url at this time
		http://www.dc2dc.com is a resller of the "other option"
 	- probably a bunch of power supp working on dc-atx convertors

> The only DC-to-DC supplies I've seen on the web seem quite expensive,
> e.g.:
>   http://www.rackmountpro.com/productsearch.cfm?catid=118

99% of the rackmount vendors are just reselling (adding $$$ to ) a power
supply manufacturer's power supply ...

	- you can save a good chunk of change by buying direct
	from the generic power supply OEM distributors 

	- somtimes as much or mroe than 50% cost savings of the cost of
	the power supply

>   http://www.mini-box.com/power-faq.htm

most of their data are measured data per their test setups
and more info about dc-dc stuff


see the rest of the +12v DC input "atx power supply" vendors


	( +12v at up to 500A or more )

> So I suspect the DC-to-DC approach would only ever make economic sense
> for large high-end clusters, those with unusual space or heat
> constraints, or the like.  But I'm still curious about the details...

dc-atx power supply makes sense when:

	- power supply heat and airflow is a problem
		or you dont like having too many power cords 
		( 400 cords vs 40 in a rack )
		- simple cabling is a big problem ( rats nest )

	- you want to reduce the costs of the system by throwing away
	un-used power supply capacity that is available with the
	traditional one power supply per 1 motherboard and peripherals
		- most power supplies used are used for maximum
		supported load (NOT a motherboard + cpu + disk + mem only)

	- you have a huge airconditioning bill problem
		- that should motivate you to find and test a system
		with "less heat generated solutions"

	- your cluster only needs to have enough power for the cpu + 1disk

	- you have a space consideration problems
		- dc-atx power supply allows 420 cpus per 42U rack
		and up to 840 cpus for front and back loaded cluster

	- on and on ...

for a typical 4U-8U height blade clusters ( 10 blades )
	- you only need one 600-800W atx power supply to drive
	the 10 mini-itx or flex-atx blades
	- cpu is 25W ?? motherboard is 25W ... 
	- disks need 1A at 12v to spin up.. normal operation current is
	80ma at 12v ... etc .. per disk specs
	- how you want to do power calculations is the trick

	10 full-tower system with a 450W power does NOT imply you';re
	using 4500W of power for 10 systems :-)

have fun

100TB - 200TB of disks per 42U racks ??  -- even more fun
	( blades are with mini-box.com's  dc-dc atx power supply )

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