On 12/11/2010 09:23, Paul Sheer wrote:
I'm surprised by your claim that Telcos don't do NTP, [...]
I'm sure many do.
My point is that, if one's starting premise is that most systems in the
world *require* second-accurate syncronization, this is simply untrue.
In fact most work perfectly well even when they drift by minutes,
and a significant portion of critical systems do drift by minutes
in practice.
In practice, these systems must not be using NFS. NFS gets crankly when
the times drift this much. Sure, it kinda works, but there's a number
of weird effects.
Also, many of these systems appear to work, where "work" is defined as
"not catastrophically fail," but a number of problems present themselves
downstream. My mail client sorts things in send time order. This means
that people whose system clock is wrong wind up out of order. I'd call
that failure, but it kinda works too.
So the magnitude of this "kinda works" degrades as the time
synchronization between systems gets worse.
This is orders of magnitude more error than any leap second.
One problem with the "kinda works" attitude is that is a barrier to
entry for people whose systems need to work correctly to a much higher
precision than "minutes". The kinda works attitude means nobody bothers
to correct aberrant behavior because it doesn't crash the system or
programs. When someone goes to deploy systems, it becomes clear that
these problems represent a "death of a thousand cuts" situation.
That's one reason why you're seeing the push back from people on this
list: many have tried to deploy systems where sub-second synchronization
was required by the application and have run into many problems...
Warner
-paul
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