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From Rob Coli <rc...@palominodb.com>
Subject Re: 1.1.1 is "repair" still needed ?
Date Wed, 10 Oct 2012 21:55:05 GMT
On Tue, Oct 9, 2012 at 12:56 PM, Oleg Dulin <oleg.dulin@gmail.com> wrote:
> My understanding is that the repair has to happen within gc_grace period.
> [ snip ]
> So the question is, is this still needed ? Do we even need to run nodetool
> repair ?

If Hinted Handoff works in your version of Cassandra, and that version
is > 1.0, you "should" not need to repair if no node has crashed or
been down for longer than max_hint_window_in_ms. This is because after
1.0, any failed write to a remote replica results in a hint, so any
DELETE should eventually be fully replicated.

However hinted handoff is meaningfully broken between 1.1.0 and 1.1.6
(unreleased) so you cannot rely on the above heuristic for
consistency. In these versions, you have to repair (or read repair
100% of keys) once every GCGraceSeconds to prevent the possibility of
zombie data. If it were possible to repair on a per-columnfamily
basis, you could get a significant win by only repairing
columnfamilies which take DELETE traffic.

https://issues.apache.org/jira/browse/CASSANDRA-4772

=Rob

-- 
=Robert Coli
AIM&GTALK - rcoli@palominodb.com
YAHOO - rcoli.palominob
SKYPE - rcoli_palominodb

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