[ntp:questions] NTP under AIX?

Greg Moeller skywise at gmail.com
Tue May 16 21:19:18 UTC 2017


On Tuesday, May 16, 2017 at 3:36:07 PM UTC-5, William Unruh wrote:
> On 2017-05-16, Greg Moeller  wrote:
> >> My semi costs $1000000 and does very heavy hauling. What do you mean I
> >> cannot enter it into the Indie 500?
> They would not allow me to do so.
Awww, I'd pay to watch that.
> 
> > Of course you can.  Will it do very well in the race?  Possibly not.  But it wouldn't have to pit so maybe it could be a tortoise/hare thing.  :)
> > You can also haul a load of merchandise to a warehouse with a panel truck or a pickup truck.  Is it very good at it?  Probably not. 
> > Is the IBM P series hardware very good at multitasking?  Yes, yes it is.  (that's what it's main/only job is)
> >> 
> 
> Precisely. It would not be very good at it. 
> 
> >> 
> >> >
> >> > Is there a way to test?  It seems like I'm heading into the unknown here.  :)
> >> 
> >> No. It is not unkown. It is well known. It is a bad idea.
> > Technically, running NTP on unix isn't a very good idea as all unix systems are multitasking and can get busy/lose time.  I suppose the question is how sloppy any given system might be.
> 
> The cpu has a cycle counter in it. That counter does not care that the
> 
> system is multitasking. Ie the time counting is not a software clock.  
> 
> Can one put a ntp onto a virtual machine. Yes. Does it give great time?
> No.
> 
> 
> > A nice oven-controlled-crystal dedicated system running a dedicated OS just for time keeping would serve the best time.
> 
> Yes. But again it depends on its time source. Using a gps receiver with
> a PPS output will give time to a few microseconds of UTC. If you are
> serious about time for your systems, get a gps. You can run a coax out
> to a window somewhere where you put the gps antenna. A hundred feet of
> coax should get you out to window-- preferably facing south with a
> realtively clear viewof the sky.  If needed you can
> compensate for the time delay along that cable ( about 1.5ns per foot if
> you require that accuracy-- you still have not told us what accuracy
> you want. ).
That would imply there are windows.  This is one of those places with trapping passages in case intruders try to storm the datacenter, windows would be a fatal weakness.  :)
> 
> Re your people-- don't call it a computer. Call it an ntp time source.
> Make a nice box for it if nessary and still come in well under the spare
> change limit in your organization.
> 
> But yes, a nice oven controlled crystal dedicated system would serve
> time best. You can buy them. Of course the time that the computers in
> your organization got from it would be much less accurate, and probably
> no worse than if youuse an RPi with a Sure GPS receiver (about $80-- 100
> with box).

I'm looking at simple stable time.  Time used to come from AD servers keeping their own time.  Standing there with a pocket watch would be an improvement over that.
Currently, we have 3 DMZ servers getting time from the internet (stratum 2 and 1), then 2 NTP servers inside the DMZ getting time from those 3 servers.  The inner environment then gets time from those two. (AD also gets it's time from the 3 DMZ servers, putting them on equal footing, stratum-wise)



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