Playing with / understanding Riak configurations

Tom Santero tsantero at gmail.com
Wed Jul 27 18:11:26 EDT 2016


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?
>
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