[Dirvish] Mac OSX and power problems and winter

Keith Lofstrom keithl at kl-ic.com
Tue Oct 31 09:13:16 PST 2006

On Tue, Oct 31, 2006 at 05:41:29PM +0100, Bernd Haug wrote:
> While the backup to UFS seemed to work well when it worked, today I
> encountered 2 kernel panics while backing up. Both messaged "bad
> dir". Last one:

What physical hardware are you using?  Type of Mac, type of backup
drive?  I understand that a Mac Mini can sometimes have overheating
problems, and something as busy as rsync could find those problems.
Is there some way to read out the temperature of the machine?

Another hazard to warn the list about:  If you are using dirvish
for small-office/home-office SOHO backups, you will sometimes
encounter problems with electric power to your computer during
the winter that can cause problems for backups.  Here in Oregon
it is starting to get cold at night, and this makes the natural
gas furnace come on in the morning.  The furnace uses a fan driven
by an older design induction motor, and when the motor starts
turning, it briefly causes line power to "sag", that is, the
voltage to drop lower than normally acceptable.  

If the computer power supply is weak, and rsync is keeping the hard
disk very busy and drawing a lot of power, then the combination of
effects can cause a computer crash and corrupt a dirvish image.  I
have not seen this destroy a disk or cause corrupted backups to be
accepted by dirvish, but it can prevent some backups from being
made (and the next night's backups take longer).  I had to adjust
the morning turn-on time for the electric thermostat, and the dirvish
startup time, so that the furnace does not turn on while dirvish is
running.  After all, I have the computers running rsync to keep the
house warm at night.


Keith Lofstrom          keithl at keithl.com         Voice (503)-520-1993
KLIC --- Keith Lofstrom Integrated Circuits --- "Your Ideas in Silicon"
Design Contracting in Bipolar and CMOS - Analog, Digital, and Scan ICs

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