[geeks] Need geek assistance

[Patrick Finnegan]

On Sunday 18 April 2010, sammy ominsky wrote:
> Jonathan Patschke wrote:
> Blades suck a lot of power for the space they're in.  We get 2x20A
>  per rack, and at the price we'd pay for additional circuits, it's
>  not possible to run a 4U blade server in the rack with anything
>  else.  I had to quote a friend who wanted to colo one with us
>  $1500/month because of the power requirements.  We run a full rack
>  of 1- and 2U servers with modern energy requirements in that same
>  cabinet.

Based on what I see at work, I don't understand how it's possible to run 
40 1U, dual-processor servers off of 2@ 120V, 20A circuits.  With the 
machines running flat-out, we can do about 12-15 dual-CPU quad-core Dell 
1950s per 30A, 208V circuit.

Also, I don't understand why anyone uses 120V power in a "datacenter" 
that has modern equipment.  Factoring in everything, it costs less to 
run a single 30A, 208 or 240V circuit instead of two 120V, 20A circuits, 
and with the higher voltage, you get less drop over the line and the 
power supplies run more efficiently.  In my "home datacenters" I don't 
bother running 120V for machines unless they won't take 240V.

Work is getting one of the HP POD "datacenter trailers" this year, as 
we're about out of space, and it runs off 415/240V (at 60Hz) which is 
supposed to be "the future" because you end up halving the current draw, 
and thus reducing power wasted in lines.

I guess the biggest problem with using 208/240V instead of 120V/20A 
circuits is that you can't just pop buy Home Depot and pick up a $5 
power strip for your "datacenter". ;)

Also, I really doubt the power usage would be as high as you claim.  
Nameplate ratings are nothing like the actual power usage of devices, 
especially with something like a blade chassis. Also, what rate in kWh 
are you charging? $1500/mo works out to $2/hr, which at 3.84kW (the max 
continuous draw you're permitted on two 120V, 20A circuits, which is 80% 
load) is over $0.52/kWh for power and cooling, which is ridiculous.

Pat
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