[VoiceOps] DST handling

David Hiers hiersd at gmail.com
Thu Nov 5 17:16:06 EST 2009

I thought that ntp doesn't know or care about DST.  It works in UTC,
and the OS is responsible for any DST adjustment it wants to make.

If you're an hour (3600 seconds) off in NTP, and it takes 2000 seconds
to adjust for every second you are off, it'll take 7200000 seconds to
get back on track, which is about 83 days.  Seems kinda long...


On Thu, Nov 5, 2009 at 1:55 PM, Peter Beckman <beckman at angryox.com> wrote:
> On Thu, 5 Nov 2009, Dan Young wrote:
>> On Thu, Nov 5, 2009 at 1:03 PM, Peter Beckman <beckman at angryox.com> wrote:
>>>  In discussing time, one of my providers avoids syncing their servers to
>>>  the correct time on an ongoing basis (i.e. with ntpd), with the argument
>>>  that if they sync during calls, billing would be wrong.  Some of there
>>>  servers therefore skew a LOT, and sometimes their call servers can be
>>> off
>>>  the real time by _HOURS_ (I suspect this is due to running Asterisk on
>>> VMs
>>>  which are notoriously bad at keeping time).  I've griped about it, but
>>>  they say they only sync the time when there are no calls at midnight,
>>>  which never happens.
>> I'm sure this isn't news to you, but... By default, ntpd will not snap
>> to a new time, but rather slew slowly towards the correct time.
>> How slowly? man 8 ntpd:
>> "about 2,000 s for each second the clock is outside the acceptable range."
>  Oh, _I_ know that.  I've tried to explain to them why this would be a good
>  thing.  Then again, I'm not sure how fast ntp can react to bad time skew
>  due to Virtual Machine kernel timing issues, might take a lot of trial and
>  error to get it right.
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