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From Marcus Eriksson <krum...@gmail.com>
Subject Re: Question on how to run incremental repairs
Date Wed, 22 Oct 2014 12:47:20 GMT
On Wed, Oct 22, 2014 at 2:39 PM, Juho Mäkinen <juho.makinen@gmail.com>
wrote:

> I'm having problems understanding how incremental repairs are supposed to
> be run.
>
> If I try to do "nodetool repair -inc" cassandra will complain that "It is
> not possible to mix sequential repair and incremental repairs". However it
> seems that running "nodetool repair -inc -par" does the job, but I couldn't
> be sure if  this is the correct (and only?) way to run incremental repairs?
>
> yes, you need to run with -par


> Previously I ran repairs with "nodetool repair -pr" on each node at a
> time, so that I could minimise the performance hit. I've understood that
> doing a single "nodetool repair -inc -par" command runs it on all machines
> in the entire cluster, so doesn't that cause a big performance penalty? Can
> I run incremental repairs on one node at a time?
>

repair still works the same way, you can do with -pr, and no, repair -inc
-par does not run on all nodes, it repairs all ranges that the node you are
executing it on owns, so, if you have rf = 3 you will need to run repair
(without -pr) on every third node

>
> If running "nodetool repair -inc -par" every night in a single node is
> fine, should I still spread them out so that each node takes a turn
> executing this command each night?
>

use your old schedule, repair works the same way, just that incremental
repair does not include already repaired sstables


> Last question is a bit deeper: What I've understood is that incremental
> repairs don't do repairs on SSTables which have already been repaired, but
> doesn't this mean that these repaired SSTables can't be checked towards
> missing or incorrect data?
>

no, if you get a corrupt sstable for example, you will need to run an old
style repair on that node (without -inc).

>

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