IP: Re: computer and telecom centers get undeserved black eye for power usage

[David Farber <dave@farber.net>]

>Date: Mon, 09 Apr 2001 07:24:04 -0700
>To: farber@cis.upenn.edu, ip-sub-1@majordomo.pobox.com
>From: "Joseph C. Pistritto" <jcp@jcphome.com>
>Subject: Re: IP: computer and telecom centers get undeserved black eye
>   for power usage
>
>I just got done ordering our data center setup at Zaplet Inc. where I used 
>to work.  The datacenter is at Equinix.
>
>We provisioned it at 2 20amp 120V circuits per rack (42U units of 
>equipment).  That's not enough for 42U of "1U" servers, but then you have 
>a huge cooling problem as well if you dump that much power into that small 
>a space.  The reason we used 2 20amp circuits was for redundency, but i 
>can see someone actually *using* that much power if they really fill up 
>the rack space (in which case you'd need to provision additional circuits 
>but not additional current draw for redundency).
>
>So assuming 20amps @ 120v = approx 2.5KW per "rack" and lets say it takes 
>*another* 2.5KW to air condition that space (which is overkill, air 
>conditioning is more efficient than resistive heating, which is 
>essentially what computers are...), that means approximately a 4 sq. foot 
>area would have 5KW of draw.  (not including corridors and such).  Or 
>2.5KW per square foot (high estimate).
>
>So that works out to:
>   1.25KW per sq. foot (high estimate for densely packed areas)
>
>We know this is high because people usually quote "available power" in the 
>200-300 watts/sq. foot range (inclusive of hallways etc.).  275watts/sq. 
>ft. is a common metric used here for power availability for 
>instance.  (your lesser dataccenters dont even have that much 
>available).  (thats direct power draw, not including airconditioning, so 
>doubling that would be approximately 0.5 KW/sq. ft.  So we can tell my 
>estimate above from our racks is high, but irrationally so for actual 
>worst case).
>
>It seems reasonable that a datacenter (aka "server farm") would ask for 10 
>megawatts of power though. (so 46 of them could well have asked for 500 
>Megawatts).  I know that *ONE* 2 million sq. ft planned facility in San 
>Jose is speced at 190Megawatts (the city council is forcing them to put in 
>a cogen plant with that capacity before building it though...)
>
>I think the 60-100KW/sq. ft. is an arithmetic error though.
>
>     -jcp-



For archives see: http://www.interesting-people.org/