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From aaron morton <aa...@thelastpickle.com>
Subject Re: nodetool repair - when is it not needed ?
Date Thu, 23 Aug 2012 09:36:13 GMT
HH works to a point. Specifically, it only collects hints for the first hour the node is down
and it has a safety valve to avoid the node collecting hints getting overwhelmed. Looking
at the code it takes a bit for that the trip and you would get a TimeoutException coming back.


Also when hints are replayed they are sent of as mutations, which may still be dropped by
the target if they are not serviced before rpc_timeout. Sending nodes throttle their requests
so it's unlikely but possible. 

HH is is much more robust, but AFAIK repair is still _the_ way to ensure on disk consistency.


Cheers

-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 23/08/2012, at 6:59 AM, Rob Coli <rcoli@palominodb.com> wrote:

> On Wed, Aug 22, 2012 at 8:37 AM, Senthilvel Rangaswamy
> <senthilvel@gmail.com> wrote:
>> We are running Cassandra 1.1.2 on EC2. Our database is primarily all
>> counters and we don't do any
>> deletes.
>> 
>> Does nodetool repair do anything for such a database. All the docs I read
>> for nodetool repair suggests
>> that nodetool repair is needed only if there is deletes.
> 
> Since 1.0, repair is only needed if a node crashes. If a node crashes,
> my understanding is that a cluster-wide repair (with -pr on each node)
> is required, because the crashed node could have lost a hint for any
> other node.
> 
> https://issues.apache.org/jira/browse/CASSANDRA-2034
> 
> =Rob
> 
> -- 
> =Robert Coli
> AIM&GTALK - rcoli@palominodb.com
> YAHOO - rcoli.palominob
> SKYPE - rcoli_palominodb


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