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From "Benjamin Lerer (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8437) Track digest mismatch ratio
Date Tue, 20 Jan 2015 17:24:35 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8437?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14284058#comment-14284058
] 

Benjamin Lerer commented on CASSANDRA-8437:
-------------------------------------------

I do not think that it is exactly the same. What we show in netstats is the number of read
repairs that are attempted and the one performed (blocking or background).
What this metric shows is the ratio: {{number of request resulting in at least one mismatch
/ number of requests}}.



> Track digest mismatch ratio
> ---------------------------
>
>                 Key: CASSANDRA-8437
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8437
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Sylvain Lebresne
>            Assignee: Benjamin Lerer
>            Priority: Minor
>             Fix For: 2.1.3
>
>         Attachments: CASSANDRA-8437.txt
>
>
> I don't believe we track how often read results in a digest mismatch but we should since
that could directly impact read performance in practice.
> Once we have that data, it might be that some workloads (write heavy most likely) ends
up with enough mismatches that going to the data read is more efficient in practice. What
we do about it it step 2 however, but getting the data is easy enough.



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