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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-4482) In-memory merkle trees for repair
Date Thu, 02 Aug 2012 14:35:02 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-4482?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13427347#comment-13427347
] 

Jonathan Ellis commented on CASSANDRA-4482:
-------------------------------------------

This is how the original Dynamo paper describes maintaining merkle trees.  The problem that
Acunu doesn't mention is that this forces you to do read and rehash all the rows sharing the
tree leaf with row X, whenever any row X is updated.  So you are trading sequential i/o for
random i/o... not a good move, unless you assume SSD or a small dataset (and even then, you're
rehashing many rows on each update, not just one).

I'm a bigger fan of the continuous repair approach enabled by CASSANDRA-3912, and discussed
in CASSANDRA-2699 (although i think 2699 overcomplicates things).
                
> In-memory merkle trees for repair
> ---------------------------------
>
>                 Key: CASSANDRA-4482
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4482
>             Project: Cassandra
>          Issue Type: New Feature
>            Reporter: Marcus Eriksson
>
> this sounds cool, we should reimplement it in the open source cassandra;
> http://www.acunu.com/2/post/2012/07/incremental-repair.html

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