In fact, some switches have a firmware toggle to reverse the fan direction.


On Thu, Oct 20, 2011 at 3:00 PM, Brian Mathis <
[email protected]> wrote:

> On Thu, Oct 20, 2011 at 2:26 PM, Luke S. Crawford <[email protected]> wrote:
> >
> > I've been mounting switches backwards forever;  I mean, the ports are on
> > the back of the servers, right?  it only makes sense.   Now, normally,
> > I put it at the top of the rack and it works fine;  excess heat gets
> > sucked out through the fan at the top of the rack.
> >
> > Well, in my most recent racks, I decided to be clever and mount it in the
> > middle.  Less cable travel for everyone, right?
> >
> > The idea turned out less brilliant than planned.   I mounted a server
> > above it that was already, ah, iffy heat wise, and as soon as it was
> > loaded, it crashed, I believe due to thermal stress.
> >
> > So my thought is to just mount some powerful fans opposite the switch[1],
> > pushing the hot air out the front of the rack.  I mean, it would warm
> > the intake of the servers above, but most of my servers are not thermally
> > iffy, and the data center is reliably cold, so that seems to be less of
> > an evil than dumping all the heat into the server immediately above
> > through the bottom of the case.  (though, I suppose, that is also an
> option;
> > I have some massively overcooled 3u chassis that could take that heat
> > and a lot more and dissipate it before anything unpleasant happened.
> > Heck, I should put the 'thermally iffy' server in a new case anyhow,
> > and that wind tunnel sounds like just the thing;)
> >
> > [1]perhaps something like this:
> > http://www.amazon.com/Tripp-Lite-SmartRack-Rack-fan/dp/B001DW8J5M
>
>
> I wouldn't consider this backward, but the correct way.  If the fans
> in the switch are blowing the wrong way, that's a design mistake made
> by whoever built the switch.
>
> The problem here is the server that's crashing.  If it crashed
> immediately then it was already far too close to thermal failure and
> you need to address that.  I'd remove the CPU coolers, clean them off,
> then remount with some fresh thermal compound.  Clean out any dust in
> the fans, make sure all fans are working, etc...
>
>
> -☙ Brian Mathis ❧-
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