On 5/1/19 5:39 PM, William Herrin wrote:
On Wed, May 1, 2019 at 12:23 PM Mehmet Akcin <mehmet@akcin.net> wrote:
I am trying to buy a GPS based NTP server like this one
https://timemachinescorp.com/product/gps-time-server-tm1000a/
but I will be placing this inside a data center, do these need an actual view of a sky to be able to get signal or will they work fine inside a data center building? if you have any other hardware requirements to be able to provide stable time service for hundreds of customers, please let me know.
You buy a powered GPS antenna for it. Which antenna depends on the cable length and type. The amplifier in the antenna amplifies the signal just enough to overcome the cable loss between the antenna and the receiver. Nice thick cables lose less signal. Dinky thin ones are easier to work with.
You sure you need a GPS NTP server? You understand that if you do, you need two for reliability right, and probably at geographically diverse locations? If you're not on an air-gapped network, consider syncing a couple head-end NTP servers against tick and tock (.usno.navy.mil, the naval observatory) and not worrying about it. One less piece of equipment to manage, update, secure, etc.
Two is not a great number. If they disagree, there is no majority clique to be found. Also, there is something to be said for using different models/vendors for the time sources. If you only have the same model from one vendor and there is a bug, you can lose all your time sources at once. The GPS week rollover happens every ~19.7 years, and when that problem hits is a function of the firmware and a manufacturing date put in the firmware. These problems can be mitigated if you have "enough" time sources for your internal NTP servers and you peer with enough other, possibly your, servers.
Regards, Bill Herrin
-- Harlan Stenn <stenn@nwtime.org> http://networktimefoundation.org - be a member!