> I clearly need three of those maser things for my network. Gives new meaning to the phrase "Set and forget". :)
-mel beckman > On May 14, 2016, at 12:40 PM, Baldur Norddahl <baldur.nordd...@gmail.com> > wrote: > >> On 13 May 2016 at 23:01, Baldur Norddahl <baldur.nordd...@gmail.com> wrote: >> >> Ok how many hours or days of holdover can you expect from quartz, >> temperature compensated quartz or Rubidium? Should we calculate holdover as >> time until drift is more than 1 millisecond, 10 ms or more for NTP >> applications? >> >> I am thinking that many available datacenter locations will have poor GPS >> signal so we can expect signal loss to be common. Some weather patterns >> might even cause extended GPS signal loss. >> >> >> > I found some data points here: https://en.wikipedia.org/wiki/Crystal_oven > > Assuming that acceptable drift is 10 milliseconds due that being the > expected accuracy from NTP. > > The common crystal oscillator can be as bad as 1E-4 => holdover time is 2 > minutes. > TCXO is listed as 1E-6 => holdover time is 3 hours. > OCXO is listed as multiple values, I will use 1E-7 => holdover time is 1 > day. > Rubidium is listed as 1E-9 => 3 months > Caesium is listed as 1E-11 => 30 years > Hydrogen Maser 1E-15 => 300 millennia > > I clearly need three of those maser things for my network. > > Regards, > > Baldur