5 ms·
I think it's a matter of price. GPS receivers are cheap and widely supported by timekeeping software. The cheapest atomic clock I can find is $1,500, but it's
by jewel 11y ago
I think it's a matter of price. GPS receivers are cheap and widely supported by timekeeping software. The cheapest atomic clock I can find is $1,500, but it's a hard thing to search for since the term is used to refer to radio-synchronized clocks.
If you did have an atomic clock in every datacenter, you'd still need to make sure that they didn't develop a problem that caused them to drift apart, and also you'd need to make sure that they were in sync with each other in the first place.
- ploxiln 11y agoit would be a real problem if they drifted at all ... that's kinda the point of atomic clocks, no?
- detaro 11y agoOf course atomic clocks drift as well, and as soon as you run multiple you have to keep that in mind. GPS (or rather a GPS-controlled quartz) is probably better quality than cheap atomic clocks. GPS is a convenient way to get well-synced precise time nearly everywhere you can see the sky.
- ploxiln 11y agoGPS satellites themselves use atomic clocks (and to find your position you use their also-broadcast orbital positions and math for the effects of relativity etc)
- detaro 11y agoYes, I'm aware. ?
- ploxiln 11y agoGPS satellites use atomic clocks which don't drift aka don't become 0.1% slower or faster than they should be. OK, technically they drift, but not enough to be noticeable by anyone. They're the standard to which other clocks are compared. According to https://en.wikipedia.org/wiki/Atomic_clock#Evaluated_accuracy https://en.wikipedia.org/wiki/Atomic_clock#Evaluated_accurac... existing atomic clocks can drift by 1 second in 100 million or 150 million years. You won't notice that in your high-speed datacenter applications over the course of a few decades. (unless perhaps if one is plain broken, and it's noticed by comparing to the others and taken out of service)
- KMag 11y agoI think you missed the word "cheap" in the GP.
- mentat 11y agoWithin their frame of reference. Many many frames exist.
- ploxiln 11y agoThat's true, but if it's sitting in your datacenter which is stably attached to some point on the surface of the earth, that's a well defined frame of reference.
- madaxe_again 11y ago$1500 is nothing if you're a telco. If cost were the reason they wouldn't blink at having five caesium fountains in each location - but as another observed it's likely about synchronicity - relativity is a problem if you're looking to have two clocks on opposite sides of the planet in perfect sync.