[mythtv-users] NTP drift...

[John Brooks]

On 10/13/06, Romain Kang <romain at kzsu.stanford.edu> wrote:
>
> -500 is the largest negative value that ntpd uses.  In short, it
> has freaked out and all bets are off.  Worse, if ntpd starts with
> such a large value, good hardware will drift off to false values.
> Every so often, when the discrepancy is large, ntpd will force a
> step correction, and the error will follow a sawtooth pattern
> over a period of several days.


Mmm. I see. I deleted the drift file, and ntpd has recreated it with 0.000;
I'm not sure what effect this will have on ntpd's performance.

The units for delay, offset, and jitter are milliseconds.  By
> comparison, my mythbox typically sees delays < 90 ms to Redhat's
> NTP server on the other side of the US, with jitter and offsets
> less than 20 ms.  If you're seeing values in the multi-second range,
> it would appear your WAN connection can't uniformly deliver NTP
> packets, certainly not along the paths to those servers.  One
> assumption in the original NTP implementation was that roundtrip
> delays were symmetric; no wonder ntpd is going insane.


Right-- I was afraid of that. I'm wondering if the fact that my torrents hog
bandwidth are affecting that.

Incidentally-- yes, I'm using a wireless network; usually, ntp works just
fine. Lately, though, the time has been a bit wacky. There's been quite a
bit of torrent activity on my end, which is making me wonder if that's
relevant.

Perhaps there's some hardware glitch on your box, but if it were
> that bad, I'd expect MythTV to be unwatchable.


MythTV, in general, runs just smoothly. Nevertheless, I'll try turning off
ntp for a few days and see how the system deals with it. If, for some
reason, I do find there's a hardware issue-- the hardware clock is just slow
or keeps resetting, for instance-- do I need to replace the motherboard? Or
can the battery on the motherboard be replaced?

Thanks again!
Jack.
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