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From "Eric Evans (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-2338) C* needs a LOCAL_QUORUM_PLUS_ONE_REMOTE consistency level
Date Wed, 16 Mar 2011 16:09:29 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-2338?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13007530#comment-13007530
] 

Eric Evans commented on CASSANDRA-2338:
---------------------------------------

AIUI, the reasoning behind the ConsistencyLevel enum was to simply things, to codify best
practice and make it easier for people to understand and do the Right Thing.  In other words,
sacrifice some flexibility in exchange for usability.  For this to work, the Right Answer
in situations like this is to tweak the RF knob to work with the available consistency options.

If consensus is that this trade-off is wrong (usability vs flexibility), then the reasonable
thing to do is eliminate ConsistencyLevel in favor of an int.

LOCAL_QUORUM_PLUS_ONE_REMOTE is a Bad Idea IMO, so is TWO and THREE.

> C* needs a LOCAL_QUORUM_PLUS_ONE_REMOTE consistency level
> ---------------------------------------------------------
>
>                 Key: CASSANDRA-2338
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2338
>             Project: Cassandra
>          Issue Type: New Feature
>            Reporter: Matthew F. Dennis
>            Priority: Minor
>
> for cases where people want to run C* across multiple DCs for disaster recovery et cetera
where normal operations only happen in the first DC (e.g. no writes/reads happen in the remove
DC under normal operation) neither LOCAL_QUORUM or EACH_QUORUM really suffices.  
> Consider the case with RF of DC1:3 DC2:2
> LOCAL_QUORUM doesn't provide any guarantee that data is in the remote DC.
> EACH_QUORUM requires that both nodes in the remote DC are up.
> It would be useful in some situations to be able to specify a LOCAL_QUORUM (for local
consistency) + "at least one remote" for durability/disaster proofing.

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