Leaving a Computer Running ?

Ted Mittelstaedt tedm at toybox.placo.com
Sun Feb 6 06:01:34 PST 2005

> -----Original Message-----
> From: owner-freebsd-questions at freebsd.org
> [mailto:owner-freebsd-questions at freebsd.org]On Behalf Of Anthony
> Atkielski
> Sent: Sunday, February 06, 2005 3:25 AM
> To: freebsd-questions at freebsd.org
> Subject: Re: Leaving a Computer Running ?
> Ted Mittelstaedt writes:
> TM> In a clean room or positive pressure network room, where there is
> TM> an extremely low level of dust, off-the-shelf computer fans will
> TM> last many years longer than fans in a typical home PC.
> What about filters?

HEPA-quality required.

  On my current FreeBSD server (not in a clean room,
> alas!), the fans that I installed have washable plastic filters, which
> removes part of the dust.

Worthless for this kind of problem.  The particles that are the problem
go right through these.

  I'd love to find disposable filters that
> capture more dust and can simply be tossed at regular intervals.
> Ideally, they wouldn't interfere with airflow too much, but I realize
> that catching all dust and maintaining airflow are almost mutually
> exclusive.

You just put in a bigger filter and more fans for that problem.

What are needed are better fans.  The old VAX/VMS systems had fans
that ran perfectly balanced, forever, even when coated with crud.

> Currently I have two 8-cm fans blowing directly past the disk
> drives, in
> order to keep them as cool as possible (not that the drives are that
> busy, but I'm trying to be prudent).
> TM> For PC's left on for long periods, they have a different problem
> TM> because disk drives that spin at full speed continuiously (as
> TM> server drives do, servers have power saving disabled on their
> TM> drives of course for obvious reasons) the disk will eventually
> TM> overheat in just about all the garden-variety case designs.
> TM> (you can fix this yourself of course, by adding more fans to
> TM> the cases)  Once the drive overheats the lubrication migrates
> TM> out of the bearings and if the drive is turned off for more
> TM> than 6-8 hours, it cools down enough to the point that the drive
> TM> will never spin up again.
> Interesting!  Have you actually had this happen?

Yes, about 6 times over the last 10 years.  All of it was crap small
minitowers or otherwise airflow-restricted cases that let the drive
heat up too hot to touch.

Sometimes hitting it with a hammer - hard - right when you apply power
will get them going again.

 I've had drives fail
> on restart but not because they wouldn't spin up (as far as I know).
> I've had drives fail very quickly when I've packed too many of
> them into
> a single case (as in weeks or months).  We needed the additional space
> and we were lucky to get the drives--asking for more fans or a better
> case or anything like that would have been an exercise in futility.

Yup, happens all the time.  You needed a Go Big Red Fan for that
(read Neal Stephenson's The Big U for an explanation)


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