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From "Jeff Jirsa"<jji...@apache.org>
Subject Re: Data Loss irreparabley so
Date Thu, 27 Jul 2017 05:48:44 GMT


On 2017-07-25 15:49 (-0700), Roger Warner <rwarner@pandora.com> wrote: 
> This is a quick informational question.     I know that Cassandra can detect failures
of nodes and repair them given replication and multiple DC.
> 
> My question is can Cassandra tell if data was lost after a failure and node(s) “fixed”
and resumed operation?
> 

Sorta concerned by the way you're asking this - Cassandra doesn't "fix" failed nodes. It can
route requests around a down node, but the "fixing" is entirely manual. 

If you have a node go down temporarily, and it comes back up (with it's disk intact), you
can see it "repair" data with a combination of active (anti-entropy) repair via nodetool repair,
or by watching 'nodetool netstats' and see the read repair counters increase over time (which
will happen naturally as data is requested and mismatches are detected in the data, based
on your consistency level).



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