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Open-sourcing a more precise time appliance

engineering.fb.com

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Re: Open-sourcing a more precise time appliance

#51

Post by tyingq »

abyagowi wrote: post #45
tyingq wrote: post #29

Earlier quoted context omitted.

Those have the external source but don't seem to have the internal reference (Rubidium, Cesium, etc) for holdover. FB seems to be claiming to have invented a PCI card that makes a commodity server into a Stratum-1 source. Meinburg sells that too, but in proprietary appliance form.

Again, invented might be too strong. This is an abstraction of what you need minimally to build a time server on an open source basis. We appreciate and are humble to other products in the market

The availability of a much cheaper product than the appliances will likely create a bit of stir with competitors. The article mentions better management functions too. So perhaps invented is too strong, but it's more notable than your follow up comments suggest.

Re: Open-sourcing a more precise time appliance

#52

Post by nefitty »

efficax wrote: post #50
nefitty wrote: post #2

I didn’t want to click this so I assume others here won’t either. Here’s the top points they highlight themselves: - Facebook engineers have built and open-sourced an Open Compute Time Appliance, an important component of the modern timing infrastructure. - To make this possible, we came up with the Time Card — a PCI Express (PCIe) card that can turn almost any commodity server into a time appliance. - With the help…

Oh no if you click it Facebook might find out! The horror

Yes, that’s why I posted that comment.

Re: Open-sourcing a more precise time appliance

#53

Post by amelius »

myself248 wrote: post #37
amelius wrote: post #35

Earlier quoted context omitted.

What sounds like the most reasonable strategy to me is to have a single atomic clock in every datacenter, and then some basic hardware in every server to communicate with it.

Which is exactly how the telephone industry has done it for decades, it's called a "building-integrated timing supply", or BITS clock. Typically this is a GPS-referenced clock with a local quartz or rubidium holdover oscillator, and output cards with dozens or hundreds of outputs serving various machines in the office.

Curious, why did telephony require such accurate clocks?

Re: Open-sourcing a more precise time appliance

#54

Post by nefitty »

the_biot wrote: post #42
nefitty wrote: post #2

I didn’t want to click this so I assume others here won’t either. Here’s the top points they highlight themselves: - Facebook engineers have built and open-sourced an Open Compute Time Appliance, an important component of the modern timing infrastructure. - To make this possible, we came up with the Time Card — a PCI Express (PCIe) card that can turn almost any commodity server into a time appliance. - With the help…

Whatever you may think of Facebook, they've done awesome things within their Open Compute Project. They also fund a lot of open source work.

Yes, I appreciate their engineering work. I did have to click the link to post my comment. I posted it for other people’s benefit because I understand the concerns regarding their privacy record.

Re: Open-sourcing a more precise time appliance

#55

Post by bob33212 »

kd913 wrote: post #11
kfreds wrote: post #5

Earlier quoted context omitted.

From the article: "More accurate time keeping enables more advanced infrastructure management across our data centers, as well as faster performance of distributed databases."

That seems rather ambiguous and doesn't really explain why having more time precision results in faster performance or 'advanced infrastructure management'. I can understand why a stock broker or trading firm requires PTP to enable precise date-stamps for auditing/validating trades. I don't see how having a time granularity on the order of picoseconds is needed for a data center.

If you know that your clocks are exactly the same in New York and Japan you can assume that if an account creation timestamp in Japan is before the account creation time in New York for the same username that the account should go to the Japan user and the New York user will be told that he cannot use that username. Previously the way to handle that problem was to have all account creation be done on one server which will block the table while it is doing writes. That doesn't scale when you need to insert millions of rows a second.

Re: Open-sourcing a more precise time appliance

#56

Post by jeffbee »

Slaving your clocks to GPS seems like it just gives the USAF space command a way to, eventually, wreck your operations. If you don’t have requirements for accuracy referenced to civil time (such as mifid 2) why wouldn’t you just go with the atomic clocks alone, with gps as an advisory-only monitoring reference?

Re: Open-sourcing a more precise time appliance

#57

Post by serf »

efficax wrote: post #50
nefitty wrote: post #2

I didn’t want to click this so I assume others here won’t either. Here’s the top points they highlight themselves: - Facebook engineers have built and open-sourced an Open Compute Time Appliance, an important component of the modern timing infrastructure. - To make this possible, we came up with the Time Card — a PCI Express (PCIe) card that can turn almost any commodity server into a time appliance. - With the help…

Oh no if you click it Facebook might find out! The horror

what do you stand to gain by belittling someone's (absolutely sane) privacy considerations regarding facebook?

Re: Open-sourcing a more precise time appliance

#59

Post by fanf2 »

michaelt wrote: post #39
rkangel wrote: post #4

I'm still unclear why they need the MAC on top of the GNSS reception. I can understand if it's just to provide holdover in event of GNSS signal loss, but they seem to be saying that it provides better precision when you've got both.

Although clock holdover might seem like a pointless feature - GPS outages are very unusual* - what holdover is mostly for is giving you time to respond if someone clumsily knocks your antenna over, or crushes your coax cable, or it gets damage that makes it fill with water, or something like that. A lot of the demand for high-precision clocks is for cell phone base stations, where there's no guarantee there'll be som…

Various militaries do regular GPS jamming exercises

https://www.ofcom.org.uk/spectrum/information/gps-jamming-ex...

https://www.navcen.uscg.gov/?pageName=gpsServiceInterruption...

Re: Open-sourcing a more precise time appliance

#60

Post by NelsonMinar »

Man, tough crowd here. And someone who's been following precise timekeeping tech for 25 years now.. this is really cool! I think it's great some smart engineers have built a new reasonably compact and low cost very precise bit of timekeeping hardware. Thank you for sharing it open source!
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