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From aaron morton <aa...@thelastpickle.com>
Subject Re: Replication factor - Consistency Questions
Date Fri, 20 Jul 2012 09:28:36 GMT
> But isn't QUORUM on a 2-node cluster still 2 nodes?
Yes.

3 is where you start to get some redundancy - http://thelastpickle.com/2011/06/13/Down-For-Me/

Cheers


-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 20/07/2012, at 10:24 AM, Kirk True wrote:

> But isn't QUORUM on a 2-node cluster still 2 nodes?
> 
> On 07/17/2012 11:50 PM, Jason Tang wrote:
>> 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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