[time-nuts] Noob question, NTP stratum 1.

[Tim Shoppa]

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 <
time-nuts at lists.febo.com> 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.
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