Uwe Klein <[EMAIL PROTECTED]> writes: >Unruh wrote: >> Uwe Klein <[EMAIL PROTECTED]> writes: >> >> >>>Unruh wrote: >>> >>>>Yes, that is with reference to the road. Car three should thus completely >>>>ignore the other two cars and use his speedometer. >>>> >>>>Ie, put up a GPS receiver with a PPS and use that as your time source, and >>>>ignore all the other ntp time sources, except perhaps as sanity checks (eg >>>>if you r speedometer breaks you should get to know about it by occasionally >>>>looking at the other cars) >> >> >>>A)One GPS to each box or >>>B) a single GPS with PPS line to all boxes? >> >> >> Whichever you want. Up to you. >> >> >>>A: >>>Doesn't that impact reliability? >> >> >>>You add the failure probability of a GPS-unit to each Box >>>where one failure will make the whole system fail. >> >> >> So, that is why ntp has backup servers. You have a single failure point >> anyway-- the network. It goes down, and nothing can get the time.
>That actually is _three_ different scenarios. >time over the network: >network fails > 1: time > 2: the system as a whole > failure of network infrastructure > thus does not add to the probability of the complete system failing. >time over PPS/GPS 1 unit with signaling to each box: >network fails > 2: the system as a whole >GPS fails > 1: time > -> the system as a whole > This adds up to a higher failure rate/probability. >time over PPS/GPS unit per box: >network fails > 2: the system as a whole >GPS fails > 1: time > -> the system as a whole > This adds up to a higher failure rate/probability. > With the added disadvantage that GPS failure overall > is single failure times number of boxes. So, put a GPS connected to each box. That will be a stratum 0 source and will be selected by ntp. If that fails, have each of the other machines as a backup. They will be stratum 1 source. Then have the system go out onto the world wide net to pool.ntp. Those will be stratum 2 or lower. Each backs up the otehr. Thus each machine will gets its time from GPS (usec precision) It that fails, they get it from the local machines ( 10s of usec precision) If that all fails they get it from the net ( ms precision) It that all fails, you are SOOL. You probably have other worries anyway. How many belts and braces you want is entirely up to you. I would have one GPS on one machine. Everything gets their time from that, unless it fails in which case pool.ntp would act as a backup. But it is entirely up to you. >uwe _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions