[ntp:questions] Number of Stratum 1 & Stratum 2 Peers

Rob nomail at example.com
Sat Dec 6 08:20:07 UTC 2014

William Unruh <unruh at invalid.ca> wrote:
> On 2014-12-05, Rob <nomail at example.com> wrote:
>> William Unruh <unruh at invalid.ca> wrote:
>>>>> For internal systems I would want four servers minimum, two on-site, and 
>>>>> two on the company WAN,
>>>> I think that is ridiculous.  Introducing too many safeguards often
>>>> results in more failures due to extra complexity in the system.
>>> The problem with two is that if oneof the servers goes nuts-- for some
>>> reason starts to give out the wrong time (ie, its time is not UTC time)
>> a. that will almost never happen
>> b. that will be caught by the monitoring (e.g. nagios) and an alert will
>>    be sent and/or the system will be shut down automatically.
> Would it not be nicer is the alert is sent, but the system still keeps
> going and not shutting down? Shutting down a system seems like a pretty
> heavy price to pay for not having three instead of 2 sources.

Not shutting down the client, shutting down the errant timeserver.
Or only its NTP service.
When you have two NTP servers and one goes nuts, just shut it down and
send an alert to the operator so it can be fixed.  The clients continue
to sync to the other server without problem.
That is so much easier than to setup 4 servers and configure them in
all clients and let the complicated voting process happen in all clients.

>>> Of course your monitoring might catch this, or it might not, depending
>>> on whether you had thought of this failure mode when you set it up. So
>>> the clients could do this for days or weeks. Now if you do not care if
>>> the time jumps around by a second, then this is fine. Some places
>>> however need better time control than that.
>> The monitoring for ntpd servers shipped by default with nagios has no
>> problem detecting this.
> And when it does, what happens-- the company goes out of business? Noone
> cares? It also sends out for coffee and doughnuts for the IT team?

It becomes clearer and clearer to me that you are an armchair theorist
that has never been in touch with a professionally managed IT environment.

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