[Beowulf] power usage

matt jones jamesjamiejones at aol.com
Sat Jul 14 02:14:28 EDT 2007


Mark Hahn wrote:

 > wouldn't it be nice to find a PSU which could simply take a 12V input?
 > battery->inverter->switchingPS->DCelectronics is kind of gross...

it's quite conceivable that this would solve problems... but you still 
have to get from LV AC to ELV DC which will still be inefficient, also, 
you would need hookups and relays for AC and DC and DC after UPS system 
for EPO, the length of DC rails would play an effect, and you are still 
going to get DC-DC inefficiencies for you 5 and 3.3V rails.

pointless ramble:
say you had 3 nodes/servers - each needing 330W full power, totalling 
990W. you have a 1000W AC-12V PSU, you would have an ~~83A 12Vrail.... 
the V.drop on that over a distance would be high and incredible 
inefficient, even with a 25mm^2 cable. and then ac-dc/dc-dc rectifiers, 
they produce alot of heat dissipation. ect ect...

i think the better way to go would be to have more LV processors on one 
board, with LV RAM ect. eg 8*quad core low voltage processors, each core 
having 2GB LV RAM. having little I/O and just networking, that way you 
concentrate just on processing... storage can be done elsewhere on a 
SAN/NAS. the node would boot diskless - using flash (USB?) as secondary 
storage if really necessary. there would be a dual input PSU, ACmains 
and DC from a local UPS... the BIOS would have to have a program to shut 
the node down on the UPS batt low. but this is like going into complete 
management of nodes/server room... power, UPS, mains, EPO, cooling, node 
turn off and WOL... all in one program (part of the job scheduler i 
should think). this would really be a step into the custom and not 
commodity hardware tho.

but yea, DC electronics is gross on a large power/ampage.
--
matt

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