Timekeeping in Datacenters
- Datacenter GNSS Time Best Practices
Eight things worth doing, from the closing slide of a talk on getting the last nanoseconds to UTC. Most cost nothing but attention, and most of the error they remove is invisible until somebody checks.
- Ways to get time into a datacenter
GNSS, a fiber from a national lab, a commercial delivery service, or NTP from the internet. Why GNSS usually wins below 100 ns, and why you want more than one.
- What makes an accurate GNSS timing receiver?
Six traits, in the order they start to matter. The last one separates a box that wants to be your master clock from a box that knows you already have a better one.
- How does GNSS holdover work?
When GNSS goes away your clock coasts on the frequency it was last told. How far it drifts is decided by your room more than your oscillator — which is why a holdover measurement and a holdover specification are different objects, and only one of them is a promise.
- How to configure antenna position for datacenter GNSS receivers?
If you don't know your exact location, you can't know the exact time — about a nanosecond of error for every foot you are off vertically. Here is how to get it right.
- How to configure feedline length for datacenter GNSS receivers?
An uncalibrated feedline is likely your largest source of error to UTC — tens of nanoseconds from a cable nobody measured. Here is how to find the number and configure it.