Playing with / understanding Riak configurations

Vikram Lalit vikramlalit at gmail.com
Wed Jul 27 18:18:37 EDT 2016


Thanks Tom... Yes I did read that but I couldn't deduce the outcome if n is
decreased. John talks about data loss, but am actually observing a
different result... perhaps am missing something!


On Wed, Jul 27, 2016 at 6:11 PM, Tom Santero <tsantero at gmail.com> wrote:

> Vikram,
>
> John Daily wrote a fantastic blog series that places your question in
> context and then answers it.
>
>
> http://basho.com/posts/technical/understanding-riaks-configurable-behaviors-part-1/
>
> Tom
>
> On Wed, Jul 27, 2016 at 4:07 PM, Vikram Lalit <vikramlalit at gmail.com>
> wrote:
>
>> Hi - I have a Riak node with n_val=3, r=2, w=2 and have just one
>> key-object stored there-in. I'm trying to test various configurations to
>> better understand the system and have the following observations - some
>> dont seem to align with my understanding so far, so appreciate if someone
>> can throw some light please... Thanks!
>>
>> 1. n=3, r=2, w=2: Base state, 1 key-value pair.
>>
>> 2. Change to n=2, r=2, w=2: When I query from my client, I randomly see 1
>> or 2 values being fetched. In fact, the number of keys fetched is 1 or 2,
>> randomly changing each time the client queries the db. Ideally, I would
>> have expected that if we reduce the n_val, there would be data loss from
>> one of the vnodes. And that for this scenario, I would still expect only 1
>> (remaining) key-value pair to be read from the remaining two vnodes that
>> has the data. Note that I dont intend to make such a change in production
>> as cognizant of the recommendation to never decrease the value of n, but
>> have done so only to test out the details.
>>
>> 3. Then change to n=2, r=1, w=1: I get the same alternating result as
>> above, i.e. 1 or 2 values being fetched.
>>
>> 4. Then change to n=1, r=1, w=1: I get 3 key-value pairs, all identical,
>> from the database. Again, are these all siblings?
>>
>> _______________________________________________
>> riak-users mailing list
>> riak-users at lists.basho.com
>> http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.basho.com/pipermail/riak-users_lists.basho.com/attachments/20160727/378be85f/attachment-0002.html>


More information about the riak-users mailing list