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Date: Wed, 16 Mar 2011 18:35:29 +0000 (UTC)
From: "Matthew F. Dennis (JIRA)" <jira@apache.org>
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Subject: [jira] Commented: (CASSANDRA-2338) C* needs a
 LOCAL_QUORUM_PLUS_ONE_REMOTE consistency level
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    [ https://issues.apache.org/jira/browse/CASSANDRA-2338?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13007615#comment-13007615 ] 

Matthew F. Dennis commented on CASSANDRA-2338:
----------------------------------------------

two of the most common requests I hear from users is specify an arbitrary number of replicas (usually two) and specify things like (at least one copy in one other DC).

In any case, I certainly wasn't trying tp advocate that LOCAL_QUORUM_PLUS_ONE_REMOTE be the only one (even though the bug came out sounding like that); it's just one of many examples of more complex scenarios that I've seen several requests for.

Making it pluggable is certainly the best long term choice.  As people develop ones that are generally useful and well written, we can just include them.

> 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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