Date: Thu, 11 Nov 1999 02:05:08 -0800 (PST) From: Bob Vaughan <techie@tantivy.stanford.edu> To: billm@danger.ms, freebsd@gndrsh.dnsmgr.net Cc: freebsd-stable@FreeBSD.ORG, stabilizer@klentaq.com Subject: Re: ethernet hard or soft failure Message-ID: <199911111005.CAA16461@tantivy.stanford.edu> In-Reply-To: <199911110903.BAA79929@gndrsh.dnsmgr.net>
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> From: "Rodney W. Grimes" <freebsd@gndrsh.dnsmgr.net>
> Subject: Re: ethernet hard or soft failure
> To: billm@danger.ms (Bill Marquette)
> Date: Thu, 11 Nov 1999 01:03:48 -0800 (PST)
> Cc: stabilizer@klentaq.com (Wayne M Barnes),
> freebsd-stable@FreeBSD.ORG (FreeBSD Stable)
> > As for heat, I'd buy that three months ago,
> > there's now so damn many fans in this case adding another one would only
> > increase noise and not help temperature and the only fan blowing out warm
> > air is the one in the power supply.
>
> Ahhh... lots of fans is not always the correct solution to thermal issues,
> especially when you let me know that they are all inlet fans except the
> one exhaust fan. You have a high positive pressure created if your inlet
> CFM exceeds your outlet CFM and this can cause really strange airflows
> inside the chassis.
>
> Also when I here ``blowing out warm air'' it does infact tell me that
> a significant temperature rise is occuring inside the chassis some place,
> and that is bad news. Proper airflow through a chassis should cause less
> than a 5 or so degree C rise. The exhaust air should not feel warm to the
> human hand, if it does something is wrong with the cooling system.
>
> You might try flipping the direction on some of your fans so that the
> number of fans blowing air out of the chassis is somewhat closer, but
> still slightly less than the number blowing in. This retains the anti-dust
> measure of having a positive pressure chassis (assuming the inlet fans
> have filters over them ;-o) and often produces much better cooling.
>
Additional thoughts on cooling..
tidy up your internal cabling.. it's hard to blow thru a forest of ribbon
cables.
make sure you have good airflow from bottom to top, and put your exhaust
fans above the inlet fans, and on opposite sides on the case.
if you can't put fans on both sides, consider internal baffles to direct
airflow across hotspots.
don't forget to check your air filters for clogging. depending on your
environment, you may want to make it a checklist item on a weekly or monthly
basis.
put a thermometer in the case.
move it around, and try to find the hot areas.
look at how your cards are arranged, and how much heat each one produces.
allow some airspace around hot cards, and try to locate them where there is
good airflow.
consider splitting the heat load across multiple chassis. I tend to put
the the cpu + cdrom in one box, and the disks in another (if using multiple
disks).
-- Welcome My Son, Welcome To The Machine --
Bob Vaughan | techie@{w6yx|tantivy}.stanford.edu | kc6sxc@w6yx.ampr.org
| P.O. Box 9792, Stanford, Ca 94309-9792
-- I am Me, I am only Me, And no one else is Me, What could be simpler? --
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