3 ms·

I was referring to the amazon time sync service which I imagine has pretty tight timing requirements (similar to spanner), not NTP. Also, how exactly would GPS

I was referring to the amazon time sync service which I imagine has pretty tight timing requirements (similar to spanner), not NTP. Also, how exactly would GPS work at scale for 10,000s of servers within 1000s of racks within a DC?

jfrunyon 5y ago
"Amazon provides the Amazon Time Sync Service, which is accessible from all EC2 instances, and is also used by other AWS services. This service uses a fleet of satellite-connected and atomic reference clocks in each AWS Region to deliver accurate current time readings of the Coordinated Universal Time (UTC) global standard through Network Time Protocol (NTP). The Amazon Time Sync Service automatically smooths any leap seconds that are added to UTC. "The Amazon Time Sync Service is available through NTP" https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/set-time.html https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/set-time...
NavinF 5y ago
As I understand it, “amazon time sync service” is just a bunch of NTP servers run by Amazon. Their ClockBound library calculates error bounds the same way you would if you were using a different NTP server: |Local Offset| + Root Dispersion + (Root Delay / 2) >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.
- deelowe 5y ago
  I see. This different than what I thought it was. If it is indeed a simple NTP server, this makes sense.
froh 5y ago
By using PTP in the data center LAN to distribute the GPS time locally. https://en.m.wikipedia.org/wiki/Precision_Time_Protocol https://en.m.wikipedia.org/wiki/Precision_Time_Protocol

jfrunyon 5y ago

"Amazon provides the Amazon Time Sync Service, which is accessible from all EC2 instances, and is also used by other AWS services. This service uses a fleet of satellite-connected and atomic reference clocks in each AWS Region to deliver accurate current time readings of the Coordinated Universal Time (UTC) global standard through Network Time Protocol (NTP). The Amazon Time Sync Service automatically smooths any leap seconds that are added to UTC. "The Amazon Time Sync Service is available through NTP" https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/set-time.html https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/set-time...

NavinF 5y ago

As I understand it, “amazon time sync service” is just a bunch of NTP servers run by Amazon. Their ClockBound library calculates error bounds the same way you would if you were using a different NTP server: |Local Offset| + Root Dispersion + (Root Delay / 2) >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.

deelowe 5y ago
I see. This different than what I thought it was. If it is indeed a simple NTP server, this makes sense.

froh 5y ago

By using PTP in the data center LAN to distribute the GPS time locally. https://en.m.wikipedia.org/wiki/Precision_Time_Protocol https://en.m.wikipedia.org/wiki/Precision_Time_Protocol