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From Robert Samuel Newson <rnew...@apache.org>
Subject Re: CouchDB and future
Date Sat, 05 Oct 2019 22:32:15 GMT
Not even that. :) If you have one node, then your dbs are N=1 even if N is set to 3 in config.
the code takes the lower of the n setting and the number of known nodes (which don't have
to be up at the time of db creation).

B.

> On 5 Oct 2019, at 21:00, Joan Touzet <wohali@apache.org> wrote:
> 
> Agree - couldn't find the reference from earlier, but I believe the
> rules should be:
> 
> If you have 1 node, set n=1.
> If you have 2 nodes, set n=2.
> If you have 3 or more nodes, set n=3.
> 
> Anything else is a special case and isn't recommended.
> 
> -Joan
> 
> On 2019-10-05 15:20, Robert Samuel Newson wrote:
>> Pulling this sentence out from much earlier in the thread;
>> 
>> "N should be set to the number of nodes."
>> 
>> That's not true and our docs should not say it today or be changed to say it in the
future.
>> 
>> N is how many copies of a document we'll maintain. If you had a 20 node cluster,
you would not want 20 copies of every document. The default of 3 copies would be sufficient
to prevent accidental loss.
>> 
>> B.
>> 
>>> On 4 Oct 2019, at 23:55, Joan Touzet <wohali@apache.org> wrote:
>>> 
>>> Thanks for the follow-up. Thinking of >1 active DB per host makes this
>>> calculation a lot more challenging.
>>> 
>>> Sounds like our recently merged default change of q=2 will be fine.
>>> 
>>> -Joan
>>> 
>>> 
>>> On 2019-10-04 17:40, ermouth wrote:
>>>> This tuned out to be interesting, results vary heavily for different
>>>> platforms.
>>>> 
>>>> I included `perftest.html` into Photon design doc. The utility gives good
>>>> insight how q,n impact doc creation, doc update, validate + update, and
>>>> viewindex create/update – for a particular CouchDB instance.
>>>> 
>>>> Common observations:
>>>> * q=1 is only ok for rare special cases (like DBs with dozen docs)
>>>> * it’s ok to have q==cores or q==cores+1 or even cores+2: write perf drops
>>>> a little, but viewindex update is bit faster
>>>> * excessive q (say, more than cores×2) negatively impacts direct write
>>>> perf: having q8 for 2core at least halves write perf for most
>>>> commodity/lean platforms and hw cfg.
>>>> 
>>>> ermouth
>>>> 
>>>> 
>>>> чт, 11 июл. 2019 г. в 18:17, Joan Touzet <wohali@apache.org>:
>>>> 
>>>>> On 2019-07-11 8:05, ermouth wrote:
>>>>>>> to help with the documentation step
>>>>>> 
>>>>>> Probably. Please give me a hint what you need.
>>>>> 
>>>>> What default settings right now are wrong for a system with low RAM,
low
>>>>> CPU, and slow disk - such as a RaspberryPi v1, or a $15/mo AWS server?
>>>>> 
>>>>> -Joan
>>>>> 
>>>>> 
>>>> 
>>> 
>> 
> 


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