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From Jason Tang <ares.t...@gmail.com>
Subject Re: Replication factor - Consistency Questions
Date Wed, 18 Jul 2012 06:50:45 GMT
Yes, for ALL, it is not good for HA, and because we meet problem when use
QUORAM, and current solution is switch Write:QUORAM / Read:QUORAM when got
"UnavailableException" exception.

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

> Thanks..but write ALL will fail for any downed nodes. I am thinking of
> QUORAM.****
>
> ** **
>
> *From:* Jason Tang [mailto:ares.tang@gmail.com]
> *Sent:* Tuesday, July 17, 2012 8:24 PM
> *To:* user@cassandra.apache.org
> *Subject:* Re: Replication factor - Consistency Questions****
>
> ** **
>
> 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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