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 <woh...@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 <woh...@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 >>>> >>>> >>> >> >
