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From "Hiller, Dean" <Dean.Hil...@nrel.gov>
Subject Re: easy repair questions on -pr
Date Tue, 02 Oct 2012 15:47:22 GMT
GREAT answer, thanks and one last questionŠ

So, I suspect I can expect those rows to finally go away when queried from
cassandra-cli once GCGraceSeconds has passed then?

Or will they always be there forever and ever and ever(this can't be true,
right).

Thanks,
Dean

On 10/2/12 9:34 AM, "Sylvain Lebresne" <sylvain@datastax.com> wrote:

>The short version is: there is 2 use case for nodetool repair:
>  1) For periodic repair of the whole cluster
>(http://wiki.apache.org/cassandra/Operations#Frequency_of_nodetool_repair)
>.
>In that case, you should run repair *with* -pr and you should run it
>on *every* node.
>  2) When a node has been down for a long time (for instance long
>enough that hints may have been dropped), and you want to repair that
>node specifically. In that case, you should run repair on that node
>only and you should use it *without* -pr.
>
>As for the gory details, nodetool repair without -pr will repair all
>the range of the node on which the repair is done. But when a range is
>repaired, it is repaired on *all* replica. In other words, a repair on
>node A will also repair parts of other nodes that share a range with
>A. That why, in the case 1) above, where you want to repair the whole
>cluster, a repair without -pr is inefficient, because if you repair A
>and B and both are replica for the same range, you will duplicate the
>work. Hence repair -pr: on one node it repair only its primary range
>(but all replica for said range), and so if you do that on every node,
>you will have effectively repair the whole cluster without having
>repaired the same range twice.
>
>> Can I run node tool ­pr repair on just 1/RF of my nodes if I do the
>>correct nodes?
>
>As it's hopefully clear from the description above, no.
>
>>  Why are the row keys still there though?
>
>http://wiki.apache.org/cassandra/FAQ#range_ghosts
>
>
>--
>Sylvain


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