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From Jason Tang <ares.t...@gmail.com>
Subject Re: Replication factor - Consistency Questions
Date Wed, 18 Jul 2012 01:24:15 GMT
Hi

I am starting using Cassandra for not a long time, and also have problems
in consistency.

Here is some thinking.
If you have Write:Any / Read:One, it will have consistency problem, and if
you want to repair, check your schema, and check the parameter "Read repair
chance: "
http://wiki.apache.org/cassandra/StorageConfiguration

And if you want to get consistency result, my suggestion is to have
Write:ALL / Read:One, since for Cassandra, write is more faster then read.

For performance impact, you need to test your traffic, and if your memory
can not cache all your data, or your network is not fast enough, then yes,
it will impact to write one more node.

BRs


2012/7/18 Jay Parashar <jparashar@itscape.com>

> Hello all,
>
> There is a lot of material on Replication factor and Consistency level but
> I
> am a little confused by what is happening on my setup. (Cassandra 1.1.2). I
> would appreciate any answers.
>
> My Setup: A cluster of 2 nodes evenly balanced. My RF =2, Consistency
> Level;
> Write = ANY and Read = 1
>
> I know that my consistency is Weak but since my RF = 2, I thought data
> would
> be just duplicated in both the nodes but sometimes, querying does not give
> me the correct (or gives partial) results. In other times, it gives me the
> right results
> Is the Read Repair going on after the first query? But as RF = 2, data is
> duplicated then why the repair?
> Note: My query is done a while after the Writes so data should have been in
> both the nodes. Or is this not the case (flushing not happening etc)?
>
> I am thinking of making the Write as 1 and Read as QUORAM so R + W > RF (1
> +
> 2 > 2) to give strong consistency. Will that affect performance a lot
> (generally speaking)?
>
> Thanks in advance
> Regards
>
> Jay
>
>
>

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