Richard B. Gilbert wrote: > BlackList wrote: >> rotor...@yahoo.com wrote: >>> Look at it this way: We produce a system (in the form >>> of a cluster) that works today, but that can drift away >>> from UTC since it currently doesn't accept any external >>> time reference. That drift isn't a huge issue, but over >>> the multi-year lifespan of the hardware, can be significant. >>> >>> If we allow the use of external NTP servers, we now have >>> opened up what was a closed system, and must prevent that >>> new input source from causing instability. ... >>> An alternate approach would be to make our cluster >>> software resilient to intra-node time variations, but it >>> was deemed simpler to use NTP to have the cluster accept >>> an external UTC source. >> <http://lopsa.org/node/1480>
The article I referenced seemed relevant to what they are attempting. <http://lopsa.org/node/1480> When the external server(s) go away, the internal servers take some number of minutes, but eventually elect a leader and settle on a usable hierarchy. They may drift in total from the absolute notion of NTP time, but they remain synchronized with each other. > There are solutions that do not require that you get time > from the internet! ... > A GPS timing receiver ... > A VLF receiver ... WWVB ... They already mentioned several times, they aren't going to go that route: >> A HW time reference isn't feasible, nor should it >> really be necessary given our modest accuracy >> requirement. >> >> Adding hardware isn't an option. >> This product exists in the field. >> >> With thousands of deployed systems, adding hardware >> simply isn't an option. >> >> Besides the issue of thousands of systems in use, >> there's the added one that we're always deployed >> under a roof, never on top of it. :) >> >> Adding hardware is not viable. Besides which, it really >> is a fairly modest requirement of time accuracy, which >> shouldn't require special hardware. >> >> And while a hardware time source would cleanly solve the >> issue, it isn't feasible to retrofit that to thousands >> of existing installations. >> Even if it were $500, there is the expense of getting it >> installed into thousands of commercial data centers. >> Which would be a logistical nightmare, given issues of >> leased spaces, being deep inside skyscrapers, etc. >> It isn't always as simple as sticking a GPS antenna >> to a window. -- E-Mail Sent to this address <blackl...@anitech-systems.com> will be added to the BlackLists. _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
