write value reality check

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write value reality check

Louis-Philippe Perron
Hi Riak people!
Here is a dumb question, but anyway I want to clear this doubt out:

What happens when a bucket has a W quorum value higher than the N number of nodes?
are writes to disk multiplied?

thanks!

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Re: write value reality check

Mark Phillips-4
Hi Louis-Philippe 

There are no dumb questions. :)

On Wednesday, June 26, 2013, Louis-Philippe Perron wrote:
Hi Riak people!
Here is a dumb question, but anyway I want to clear this doubt out:

What happens when a bucket has a W quorum value higher than the N number of nodes?
are writes to disk multiplied?


Precisely. For example, if you run a one node Riak cluster on your dev machine you'll be writing with a N val of 3 and W of 2 by default. In other words, Riak will always attempt to satisfy the W value regardless of physical node count. 

Hope that helps. 

Mark 
 
thanks!

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Re: write value reality check

Louis-Philippe Perron
So if I get you right and extrapolate with the replication documentation page, can I say that on a 2 nodes cluster, with a bucket set to N=3 and W=ALL, my writes would be written 3 times to disk? (and with no guarantee to be on different nodes)?

thanks! 

On Wed, Jun 26, 2013 at 8:17 PM, Mark Phillips <[hidden email]> wrote:
Hi Louis-Philippe 

There are no dumb questions. :)

On Wednesday, June 26, 2013, Louis-Philippe Perron wrote:
Hi Riak people!
Here is a dumb question, but anyway I want to clear this doubt out:

What happens when a bucket has a W quorum value higher than the N number of nodes?
are writes to disk multiplied?


Precisely. For example, if you run a one node Riak cluster on your dev machine you'll be writing with a N val of 3 and W of 2 by default. In other words, Riak will always attempt to satisfy the W value regardless of physical node count. 

Hope that helps. 

Mark 
 
thanks!


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Re: write value reality check

Justin Sheehy
Hi, Louis-Philippe.

With a 2-node cluster and N=3, each value will be written to disk a total of three times: twice on one node, once on the other. (The W setting has no effect on the number of copies made or hosts used.) That behavior might seem a bit strange, but it's a strange configuration to run Riak on only two machines while asking it to store data on three of them.

The standard settings and behavior of Riak are generally optimized for non-tiny clusters, and make much more sense when there are at least five machines.

I hope this helps with your understanding.

-Justin



On Jun 28, 2013, at 10:54 AM, Louis-Philippe Perron wrote:

> So if I get you right and extrapolate with the replication documentation page, can I say that on a 2 nodes cluster, with a bucket set to N=3 and W=ALL, my writes would be written 3 times to disk? (and with no guarantee to be on different nodes)?
>
> thanks!
>
> On Wed, Jun 26, 2013 at 8:17 PM, Mark Phillips <[hidden email]> wrote:
> Hi Louis-Philippe
>
> There are no dumb questions. :)
>
> On Wednesday, June 26, 2013, Louis-Philippe Perron wrote:
> Hi Riak people!
> Here is a dumb question, but anyway I want to clear this doubt out:
>
> What happens when a bucket has a W quorum value higher than the N number of nodes?
> are writes to disk multiplied?
>
>
> Precisely. For example, if you run a one node Riak cluster on your dev machine you'll be writing with a N val of 3 and W of 2 by default. In other words, Riak will always attempt to satisfy the W value regardless of physical node count.
>
> Hope that helps.
>
> Mark
> twitter.com/pharkmillups  
>  
> thanks!
>
> _______________________________________________
> riak-users mailing list
> [hidden email]
> http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com


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Re: write value reality check

Louis-Philippe Perron
so would it make more sense to have the N=2?
I'd like to be on the safe side, after reading "There are no guarantees that the three replicas will go to three separate physical nodes" in the replication docs I started to worry about the reliability of a 2 nodes N=2 setting.

On Fri, Jun 28, 2013 at 11:06 AM, Justin Sheehy <[hidden email]> wrote:
Hi, Louis-Philippe.

With a 2-node cluster and N=3, each value will be written to disk a total of three times: twice on one node, once on the other. (The W setting has no effect on the number of copies made or hosts used.) That behavior might seem a bit strange, but it's a strange configuration to run Riak on only two machines while asking it to store data on three of them.

The standard settings and behavior of Riak are generally optimized for non-tiny clusters, and make much more sense when there are at least five machines.

I hope this helps with your understanding.

-Justin



On Jun 28, 2013, at 10:54 AM, Louis-Philippe Perron wrote:

> So if I get you right and extrapolate with the replication documentation page, can I say that on a 2 nodes cluster, with a bucket set to N=3 and W=ALL, my writes would be written 3 times to disk? (and with no guarantee to be on different nodes)?
>
> thanks!
>
> On Wed, Jun 26, 2013 at 8:17 PM, Mark Phillips <[hidden email]> wrote:
> Hi Louis-Philippe
>
> There are no dumb questions. :)
>
> On Wednesday, June 26, 2013, Louis-Philippe Perron wrote:
> Hi Riak people!
> Here is a dumb question, but anyway I want to clear this doubt out:
>
> What happens when a bucket has a W quorum value higher than the N number of nodes?
> are writes to disk multiplied?
>
>
> Precisely. For example, if you run a one node Riak cluster on your dev machine you'll be writing with a N val of 3 and W of 2 by default. In other words, Riak will always attempt to satisfy the W value regardless of physical node count.
>
> Hope that helps.
>
> Mark
> twitter.com/pharkmillups
>
> thanks!
>
> _______________________________________________
> riak-users mailing list
> [hidden email]
> http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com



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