| Re: [chrony-users] Synchronizing PHCs in addition to system clock |
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On Tue, Apr 16, 2019 at 04:05:52PM -0500, Erik Rigtorp wrote:
> > 3) new option to synchronize a PHC instead of the system clock,
> > replacing it in all time operations
> > - worse accuracy with sources on interfaces not using the specified
> > PHC (no kernel timestamping)
> > - separate chronyd instance (using PHC refclock) is needed for
> > synchronization of the system clock
> >
>
> This would work well when you have a primary interface / PHC combo with
> access to the NTP sources. But what about synchronizing the other PHCs in
> the system to the reference source?
They could be synchronized by other chronyd instances (or phc2sys from
linuxptp).
> It seems to me that case 1) would be most generally useful despite the
> lower accuracy. For most cases of 3) (single grandmaster over LAN) it would
> be possible to deploy PTP instead.
PTP requires (expensive) switches with PTP support to perform well,
and there may be other reasons beside resiliency to prefer NTP, e.g.
security.
--
Miroslav Lichvar
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