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From Pierre-Yves Ritschard <...@spootnik.org>
Subject Re: restoring a counter
Date Thu, 26 Jul 2012 17:22:30 GMT
<mdione.ext@orange.com> writes:


>> restoring a counter column family. I have two questions related to
>> this:
>> 
>>   a) how does that setting affect C* in a non-restoring start?

renew_counter_id regenerates a new "NodeId" for the cassandra VM which
is used to keep track of the counter shards the node holds. If you
regenerate node ids on each restart, you will most likely corrupt your
counter data.

>> 
>>   b) if it's < bad > (for some value of that), should I stop C*+remove
>> the setting+start C* after the value has been repaired?

This is not necessary, provided you run repair once cassandra has restarted

>> 
>>   c) bonus question: wouldn't it be nice to change the init.d script to
>> be able to add this kind of one-time settings?
>

This is possible through environment variables: env
JVM_OPTS="-Dcassandra.renew_counter_id=true" service cassandra start (at
least on the init script which comes with the cassandra debian package).

>   And a fourth one:
>
>   d) how would you restore from a full cluster crash? Assuming that I have 
> snapshots done at ~the same time.
>

If you want point-in-time restore, reprovisioning snapshots should
suffice. The node id regeneration is supposed to be used in scenarios
where data corruption occured.


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