Real ntpd uses a drift file to track the local processor's frequency offset and has a good estimate of processor clock drift after a day of tracking.
The Raspberry Pi processor clock, like any motherboards', will often be off by off anywhere from +/-200ppm but the good news is that it usually varies by less than +/-10ppm over a day and ntpd does a good job tracking this and using the drift correction during no-signal periods. +/-10ppm over 24 hours is about +/-1 second. I would strongly discourage using a Raspberry Pi in any not-just-for-fun application. I have had very poor luck keeping even brand-name hi-grade microSD cards working for a year in 24x7 Raspberry Pi hardware. No-name or store brand microSD cards seem to barely work at all when new. Unless your server farms are completely isolated from the internet at large, you should consider using a curated list of public NTP sources. Tim N3QE On Mon, Jul 22, 2019 at 10:05 AM wildylion via time-nuts < [email protected]> wrote: > Hello there, > > I wanted to ask for advice regarding NTP > > Situation 1: > What I currently have is a uBlox M8N GPS puck I'm planning to use with the > Raspberry PI. Seems like it should work almost out of the box with some > kernel tuning, but I have a question about short term stability in the > event of GPS loss - how well will the board hold over if it's lost GPS for, > say, 24 hours? > > Situation 2: > Also, there's a need for more dependable NTP time sources for our > colocated spaces. > > What we have is about 100 servers, some of them running DBMS that wouldn't > like clock drift at all. After a recent incident involving NTP I've got an > idea to install GPSDO time servers in each datacenter and slave them to > stratum2's that will be actually distributing time to clients. > > All the certified GNSS disciplined clocks are really expensive (way more > than the management would approve), so what I'm planning to do is possibly > getting a couple LeoNTP units and using them as the root time sources, > would this be a good plan? Of course, all the NTP infrastructure will be > monitored, and possibly we'll use Stratum 2 servers which would be slaved > to GPSDO S1's AND the public NTP pool for sanity checks. > > Maybe BG7TBL's units instead of LeoNTP? > Is that a good idea? > > Sent with [ProtonMail](https://protonmail.com) Secure Email. > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
