Or use spotify’s reaper and forget about it
https://github.com/spotify/cassandra-reaper
<https://github.com/spotify/cassandra-reaper>
> On Apr 13, 2015, at 3:45 PM, Robert Coli <[email protected]> wrote:
>
> On Mon, Apr 13, 2015 at 3:33 PM, Jeff Ferland <[email protected]
> <mailto:[email protected]>> wrote:
> Nodetool repair -par: covers all nodes, computes merkle trees for each node
> at the same time. Much higher IO load as every copy of a key range is scanned
> at once. Can be totally OK with SSDs and throughput limits. Only need to run
> the command one node.
>
> No? -par is just a performance (of repair) de-optimization, intended to
> improve service time during repair. Doing -par without -pr on a single node
> doesn't repair your entire cluster.
>
> Consider the following 7 node cluster, without vnodes :
>
> A B C D E F G
> RF=3
>
> You run a repair on node D, without -pr.
>
> D is repaired against B's tertiary replicas.
> D is repaired against C's secondary replicas.
> E is repaired against D's secondary replicas.
> F is repaired against D's tertiary replicas.
> Nodes A and G are completely unaffected and unrepaired, because D does not
> share any ranges with them.
>
> repair with or without -par only covers all *replica* nodes. Even with
> vnodes, you still have to run it on almost all nodes in most cases. Which is
> why most users should save themselves the complexity and just do a rolling
> -par -pr on all nodes, one by one.
>
> =Rob
>
