[ntp:questions] The libntp resumee...

Ryan Malayter malayter at gmail.com
Mon Oct 13 13:30:22 UTC 2008

On Tue, Sep 9, 2008 at 2:52 PM, Richard B. Gilbert
<rgilbert88 at comcast.net> wrote:
> FWIW, a system that has been
> synchronized by NTP will tend to stay close to the correct time for a
> reasonable period of time as long as the environment does not change
> significantly.  If the network fails AND the air conditioning fails you
> are in trouble!

That is, of course, precisely what happens in many long-term power
outages. Typical UPS battery run times in a datacenter are in minutes,
not hours. And UPS rarely backup the cooling system. If you don't have
a working generator on standby with plenty of fuel, you're up the
proverbial creek.

Even if you have the generators, you have to be careful. A colocation
provider recently had an outage that was interesting. A truck ran into
their (exterior) transformers, cutting utility power. No problem, they
have generators, right?. Well, their water chillers could not re-start
fast enough after the generators came on line, so the rapidly
increasing temperature caused shut down about 1/3 of the servers in
their datacenter. All told, their SLA credits amounted to millions of

Focusing on extreme redundancy for one piece of your infrastructure
(time) is sort of pointless if you don't have full tested redundancy
in the lower layers of the system (physcial plant, power, cooling,
network, etc.)

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