[Beowulf] delayed savings time crashes
florent.calvayrac at univ-lemans.fr
Wed Apr 12 12:12:16 PDT 2006
David Kewley wrote:
>The reboots were due to a City of Pasadena power glitch at 9:17 that
>morning. :) It was raining, and a 34kV city feeder line that runs between
>the generating plant at the entrance of the 110 and a substation at Del Mar
>& Los Robles faulted. The responsible breaker took 13 cycles to break,
>during which time the single-phase voltage seen at Caltech dropped to about
>induce massive 12Hz oscillations on the room's power lines.
>As for the time glitch, that is probably induced by the fact that Daylight
>Savings Time changes only take place on the "system" clock, and in a
>standard Red Hat system those changes only get synced to the hardware clock
>upon a clean shutdown. So if your machine crashes after a DST change, then
>upon bootup syslogd gets its time from the hardware clock, which is wrong.
>The system clock is only corrected later in the bootup sequence, when ntpd
>starts. The best solution is probably to set the hardware clock to UCT
>rather than local time. UCT doesn't undergo step changes like most
>timezones in the U.S. do, so the compensation for DST happens dynamically
>in software, rather than requiring a hardware clock change.
Why don't you use a line conditioner ? It's much cheaper than a similar
UPS ($1000 for 10kW), many UPS dont guarantee voltage and waveform excepted
during clean power cuts, anyway.
A line conditioner is very handy in time of brownouts like during August
We have a Salicru one on our cluster and have a much better MTBF on our
compute nodes in comparison
with the ones of a computing room nearby.
Besides, I was confronted with the same problem about daylight saving time.
Just added a
after the NTP synchronization in cron.daily so that the time would be
on the hardware clock. (which is automatic on Windows btw).
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