Also, how exactly would GPS work at scale for 10,000s of servers within 1000s of racks within a DC?
"The Amazon Time Sync Service is available through NTP"
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/set-time...
>how exactly would GPS work at scale for 10,000s of servers
GPS module (+ GPSDO + Rb clock optional) -> SBC running NTP server -> machines running NTP client
I’m not sure what you meant by “clocks on the system board” but if you’re talking about the system clock on the NTP server or the NTP client, it really doesn’t matter. Any old crystal on the NTP server is accurate enough to stay locked to a PPS input. The clients are limited by NTP so their clocks don’t really matter either.
https://en.m.wikipedia.org/wiki/Precision_Time_Protocol
With that underneath you need just one gps clock reciever for the whole LAN, and PTP capable Ethernet adapter and switches throughout, of course. Which most are, these days.
At home, I already have a GPS module with its PPS pin connected to an Pi running an NTP server. In my data center, I use clock.sjc.he.net and that's about as good as NTP gets. Certainly good enough for one-way latency measurements.
Are there any SBCs with hardware timestamping and a PPS input? I've heard mixed reviews of the BeagleBone Black as a PTP server. Then again, even if I get that working I have no way to run PTP in the data center since there's no GPS reception in the cabinets.
