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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (CASSANDRA-5419) Employ column differencing (as done for read repairs) during node repairs
Date Tue, 02 Apr 2013 21:05:15 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-5419?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jonathan Ellis resolved CASSANDRA-5419.
---------------------------------------

    Resolution: Duplicate

Detecting diffs smaller than a row is actually the hard part.  (See link.)
                
> Employ column differencing (as done for read repairs) during node repairs 
> --------------------------------------------------------------------------
>
>                 Key: CASSANDRA-5419
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-5419
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 1.1.10
>         Environment: Production
>            Reporter: Ahmed Bashir
>              Labels: compaction, repair
>
> In particular for wide rows, the headroom required for node repairs can be substantial
given that entire rows are streamed for any and all row hash discrepancies.
> This headroom must be sustained until compaction slowly compacts these newly streamed
SSTables and reduces the overall load on each instance.
> The overall footprint of node repairs would be greatly reduced if we employed differencing
at the column level and sent over row mutations, similar to what is done during read repair.
 This is a great alternative for deployments wherein sending over entire rows rather than
the deltas is not an option.  
> Since node repairs can now specify start and end tokens (i.e. subrange repairs), the
additional computation can be broken down easily, and it's a welcome trade-off for significantly
less streaming, compaction, and temporary headroom requirements.

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