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From Jack Krupansky <jack.krupan...@gmail.com>
Subject Re: Consistency Level (QUORUM vs LOCAL_QUORUM)
Date Mon, 28 Mar 2016 03:44:58 GMT
The third choice is EACH_QUORUM which assures QUORUM in each data center
(all data centers.)

There is no "immediate consistency" per se in Cassandra. Cassandra offers
"eventual consistency" and "tunable consistency" or the degree of immediate
consistency, which is the CL that you specify - you specify the degree of
immediate consistency that you require. If you want the full immediate
consistency of a traditional relational database, then go with CL=ALL,
otherwise, take your pick from the many degrees of immediacy that Cassandra
offers:
http://docs.datastax.com/en/cassandra/3.x/cassandra/dml/dmlConfigConsistency.html
.

In short, Cassandra does indeed guarantee the degree of immediate
consistency that you specify (and presumably want.)


-- Jack Krupansky

On Sun, Mar 27, 2016 at 6:36 PM, Harikrishnan A <hari_ka@yahoo.com> wrote:

> Hello,
>
> I have a question regarding consistency Level settings in a multi Data
> Center Environment.  What is the preferred CL settings in this scenario for
> an immediate consistency , QUORUM or LOCAL_QUORUM ?
>
> If the replication Factor is set to 3  each ( 2 Data Centers) , the QUORUM
> ( writes/read) waits for 2 consistent response from nodes across the
> cluster ( out of total 6 replications) , where as LOCAL_QUORUM expects 2
> consistent response from 3 replicas within that LOCAL data Center.  If my
> above understanding is correct, does that mean QUORUM doesn't guarantee
> Immediate consistency ( in this multi Data Center Scenario) where as
> LOCAL_QUORUM does guarantee the immediate consistency.
>
>
> Thanks & Regards,
> Hari
>
>
>

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