On 2010-03-19, Dave Hart <[email protected]> wrote: > On Mar 19, 18:21?UTC, a xs4all user wrote: >> Of course you should not configure them to follow another in both directions. >> When the second computer follows the first, there is nothing instable >> or wrong going on. ?You can even pick the computer that has the most >> stable clock before configuring them. > > That's tricky without internet or other access to a stable frequency > source. The machines in question do not and never will have access to > the internet.
So just pick one randomly, or because you like its colour .. > >> He only requires the time to be the same on both computers. ?There is >> nothing that a GPS receiver will add to the system to make this easier >> than without it. ?But of course it adds complexity and requirements. > > There's one thing -- irrelevant if w32 time sync is close enough, but > ntpd has a 500ppm limit on frequency correction. Depending on the > number of machines (two here) and each machine's normal frequency > error, it may be necessary to get the source machine's frequency > closer to correct to bring it in the range the other can correct. > This is unlikely to be a problem with a couple of machines each within > 125ppm, for example, but get unlucky with a few hundred ppm positive > on one and negative on the other, or add more machines to the brew, > and your chances of having problems using an errant frequency standard > (the source machine's uncorrected clock) go up. That 500PPM was chosen as a sufficiently large value that no standard machine should come close. For a while the linux kernel time standardizing routine really screwed up and you would have machines which were 100-200 PPM out. But that has now I believe been fixed. Ie, this should not be a problem. _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
