[rescue] Deciding how to place machines in a rack...

Robert Darlington rdarlington at gmail.com
Wed Mar 5 15:52:09 CST 2008

Oh man, everyone at a previous job (national lab) would insist on
putting spaces between servers until I ran a simulation with COSMOS
FlowWorks and showed them their mistakes.  This is terrible for
cooling systems.  You guys are absolutely right about dead air space
insulating the heck out of machines.  The only way this makes sense is
if you have forced air coming from the front of the rack, such as a
fan or chiller unit.

Nevermind you waste a lot of rack space when you leave gaps between servers.


On Wed, Mar 5, 2008 at 2:40 PM, Steve Hatle <shatle at nfldinet.com> wrote:
> On 3/5/08 3:21 PM, "Patrick Finnegan" <pat at computer-refuge.org> wrote:
>  > On Wednesday 05 March 2008, Earl Baugh wrote:
>  >> I'll space each machine 1U apart, but I have a question regarding
>  >> that.
>  >
>  > FWIW, I'd suggest making the machines as contiguous as possible,
>  I think I'd agree with Pat on this one; I can't see any advantage of getting
>  air between the systems. The little cooling you would get would be radiant,
>  and unless you are forcing air through those spaces, it would be minimal.
>  The machines (should) be designed to pull the air they need through them,
>  whether from the front or side as the case may be.
>  As far as using the plexi door, we did an experiment with some of our gear
>  at a previous job. These machines (Proliants) drew air from the front, and
>  exhausted from the rear. Air was forced up from the floor under and in front
>  of the racks. No top fans in the racks.
>  We used the plexi doors on the front of the racks and used the built-in temp
>  monitoring in the machines to get a baseline of internal temps. The plexi
>  doors did have some venting in them, but not much.
>  We then switched them for the mesh doors that went on the back of the racks,
>  and left the backs open. The internal temps of the machines went down
>  between 0 and 10 degrees F, without any other changes to the environment,
>  etc.
>  These were 42U racks with the machines and disk trays stacked from bottom to
>  top with no spaces in between. Never even considered that airspace between
>  would be necessary- besides, I needed every U of rack space.
>  So- I don't know how that might effect your decision. I'd say if you like
>  the plexi door, then use it. If you think 10 degrees is worth it, then you
>  can modify the door to suit.
>  Besides, the blinky lights are brighter without the door if it's
>  colored/smoked plexi :-)
>  Steve
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