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From AJ ...@dude.podzone.net>
Subject Re: Is LOCAL_QUORUM as strong as QUORUM?
Date Thu, 23 Jun 2011 00:56:39 GMT
On 6/22/2011 6:50 PM, AJ wrote:
> On 6/22/2011 5:56 PM, mcasandra wrote:
>> LOCAL_QUORUM gurantees consistency in the local data center only. Other
>> replica nodes in the same DC and other DC not part of the QUORUM will be
>> eventually consistent. If you want to ensure consistency accross DCs 
>> you can
>> use EACH_QUORUM but keep in mind the latency involved assuming DCs 
>> are not
>> located within short distance.
>>
>> -- 
>> View this message in context: 
>> http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/Is-LOCAL-QUORUM-as-strong-as-QUORUM-tp6506592p6506621.html
>> Sent from the cassandra-user@incubator.apache.org mailing list 
>> archive at Nabble.com.
>>
>
> Thanks mcasandra.
>
> I would like to know the minimal consistency_level to assure absolute 
> consistency with a multiple data center setup for minimal latency.  
> Just as quorum read/writes is the minimal needed to assure consistency 
> with a single data center cluster, what is the equivalent read/write 
> consistency_level value pair with a multi data center environment?
>
> I'm thinking... writes at EACH_QUORUM and reads at LOCAL_QUORUM?  This 
> will handle when a data center gets partitioned.   The write will fail 
> if the dc's get partitioned.  If the partition happens after a 
> successful write, then that's ok and a local quorum is all that's 
> needed for a subsequent read that's consistent.
>
I meant to say "This will handle when *two or more data centers get* 
partitioned.  The write...".

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