data center loading (was:Re: rack power question)

Wed Mar 26 15:03:06 UTC 2008

At 10:15 AM 3/26/2008, Lamar Owen wrote:
>One thing I haven't seen discussed, though, is the other big issue with
>high-density equipment, and that is weight.
>
>Those raised floors have a weight limit.  In our case, our floors, built out
>in the early 90's, have a 1500 lb per square inch point load rating, and
>7,000 pound per pedestal max weight.  The static load rating of 300 pounds
>per square foot on top of the point load rating doesn't sound too great, but
>it's ok; we just have to be careful.  Our floors are concrete-in-steel, on 24
>inch pedestals, with stringers.

I don't know about others, but we don't use raised floors. If you 
look at the airflow required and how high your raised floor actually 
has to be (5-6 ft) in our case, it simply doesn't make sense. We use 
doors at the ends of aisles, blanking panels, and a lexan cover over 
all aisles. We sequester all air and force the air to flow through 
the equipment. This typically cuts energy used for cooling roughly by 
30-45% We have seen dual 20 ton Lieberts used for a double row 
(typically 20-22 racks per row) actually cycle on and off once air is 
no longer allowed to mix. We typically will also use two Challenger 
3000 5 ton units in the middle of the row for a total of 50 tons of 
cooling and about 150KW of electrical use for 35-40 cabinets. That is 
a mix of some cabinets with fewer servers and some with high density 
10 slot dual quad core blade chassis units. We also like to build our 
datacenters on 8-12" slabs at or slightly above ground level so we 
don't really need to worry about weight loads either. Not possible if 
you are on the 20th floor of headquarters, but something to consider 
when talking about greenfield datacenter development.

-Robert

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