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From Joan Touzet <woh...@apache.org>
Subject Re: CouchDB and future
Date Sat, 05 Oct 2019 20:00:31 GMT
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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