Routers in Data Centers

Joel Jaeggli joelja at
Sun Sep 26 18:09:24 UTC 2010

Joel's widget number 2

On Sep 26, 2010, at 10:47, Chris Adams <cmadams at> wrote:

> Once upon a time, Joel Jaeggli <joelja at> said:
>> On Sep 26, 2010, at 8:26, Chris Adams <cmadams at> wrote:
>>> There are servers and storage arrays that have a front that is nothing
>>> but hot-swap hard drive bays (plugged into backplanes), and they've been
>>> doing front-to-back cooling since day one.  Maybe the router vendors
>>> need to buy a Dell, open the case, and take a look.
>> The backplane for a sata disk array is 8 wires per drive plus a common power bus.
> Server vendors managed cooling just fine for years with 80 pin SCA
> connectors.  Hard drives are also harder to cool, as they are a solid
> block, filling the space, unlike a card of chips.

It's the same 80 wires on every single drive in the string.

There are fewer conductors embedded in 12 drive sca backplane as there are in a 12 drive sata backplane, in both cases they are generally two layer pcbs. Compared to what 10+ layer pcbs that are a approaching 1/4" thick on the router. 

Hard drives are 6-12w each, a processor complex that's north of 200w per card is a rather different cooling exercise.  

> I'm not saying the problems are the same, but I am saying that a
> backplane making cooling "hard" is not a good excuse, especially when
> the small empty chassis costs $10K+.
> -- 
> Chris Adams <cmadams at>
> Systems and Network Administrator - HiWAAY Internet Services
> I don't speak for anybody but myself - that's enough trouble.

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