[ntp:questions] which servers should be peers?

unruh unruh at invalid.ca
Wed Sep 18 22:09:07 UTC 2013


On 2013-09-18, Maria Iano <maria at iano.org> wrote:
>>  I would be inclined to simply point each S2 server to an S1 in all centers, and  an S2 in all centers. If any or all the S1s start serving rubbish, they will be declared false tickers and the remaining S2s will form an acceptable service with the server with the most stable clock being selected.   Clients could do the same. However, in this worst case, unless you have some backup that can be traced to UTC (for example having your S2 farm having an access to the pool), then all your client / server farm will inevitably drift from legal time until you replace the defective S1s. 
>> 
>> Mike
>
> Thank you for your help Mike. I'd like to make sure I understand you correctly. I think you are saying you would peer a stratum 2 server with exactly one other stratum 2 server in each data center, which together with the stratum 1 servers would bring the total of peers to 8 for each stratum 2. Is that correct?
>

Well, there is a problem. You said that  you had seen all of your S1
servers suddenly declare that the time was 1982 and presumably that the
times were very close (to less than a second). They would then form a
group of servers which could well outvote the S2s that are delivering
the correct time. If you really have a failute mode like that, then you
will be screwed and you will need to include some outsiders to break the
potential tie. 

Such a unified crazyness really needs to be looked into. Why in the
world did they all go nuts at the same time?


> Thank you for the note about including an external ntp pool. I am going to look into how to get the necessary permissions and will set that up too.
>
> Merci,
> Maria
>



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