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.
uwe
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