[jira] [Issue Comment Edited] (CASSANDRA-2494) Quorum reads are not consistent

["Stu Hood (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-2494?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13023116#comment-13023116 ] 

Stu Hood edited comment on CASSANDRA-2494 at 4/22/11 6:05 AM:
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W plus R must be _greater than_ N for consistency.

EDIT: And adding a blocking implicit write step to QUORUM reads by waiting for read repair is not reasonable.

      was (Author: stuhood):
    W plus R must be _greater than_ N for consistency.
  
> Quorum reads are not consistent
> -------------------------------
>
>                 Key: CASSANDRA-2494
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2494
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Sean Bridges
>
> As discussed in this thread,
> http://www.mail-archive.com/user@cassandra.apache.org/msg12421.html
> Quorum reads should be consistent.  Assume we have a cluster of 3 nodes (X,Y,Z) and a replication factor of 3. If a write of N is committed to X, but not Y and Z, then a read from X should not return N unless the read is committed to at  least two nodes.  To ensure this, a read from X should wait for an ack of the read repair write from either Y or Z before returning.
> Are there system tests for cassandra?  If so, there should be a test similar to the original post in the email thread.  One thread should write 1,2,3... at consistency level ONE.  Another thread should read at consistency level QUORUM from a random host, and verify that each read is >= the last read.

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