[ntp:questions] question regarding NTP configuration for clusters, and "cluster time" stability

rotordyn@yahoo.com rotordyn1 at gmail.com
Tue Sep 29 21:00:50 UTC 2009


On Sep 29, 4:12 pm, Unruh <unruh-s... at physics.ubc.ca> wrote:

> Oddly enough, making sure that all of the computers are synchronized to
> UTC is probably the best way to ensure that they are all synchronized to
> each other.

Perhaps, but I haven't sorted out a way to achieve that with the
reference
NTP implementation, at least in a configuration that has redundancy
built-in. Picking one node to be the root of the internal ntp
heirarchy is
straightforward enough, but then I have to manage failover myself.

I can do that too, but I run into chicken and egg issues, in that the
cluster software needs the nodes to be in synch before starting,
so NTP must already be running.

> For example, you could run a PPS line to each computer's
> parallel port and use the interrupt from that to sync that computer to
> that PPS. Or you could sync a bunch  of them to their own PPS source (
> eg a number of gps).

With thousands of deployed systems, adding hardware simply
isn't an option.

> If the peer looses it external utc reference you could always have it up
> its level, so the rest would stop using it as a reference.

That's an interesting idea. Is there a way to implement that as a
configuration
option, or is that something I'd have to code myself? (The latter is
ok if necessary)

> One of the advantages of GPS is that it too exists in the field. And on
> house tops, and in the canyons ( well at least rooftops) of the concrete
> jungle.

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. :)

thanks,
tim





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