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From "Takenori Sato(Cloudian)" <ts...@cloudian.com>
Subject Re: -pr vs. no -pr
Date Fri, 01 Mar 2013 00:58:18 GMT
Hi,

Please note that I confirmed on v1.0.7.

 > I mean a repair involves all three nodes and pushes and pulls data, 
right?

Yes, but that's how -pr works. A repair without -pr does more.

For example, suppose you have a ring with RF=3 like this.

A - B - C - D - E - F

Then, a repair on A without -pr does for 3 ranges as follows:
[A, B, C]
[E, F, A]
[F, A, B]

Among them, the first one, [A, B, C] is the primary range of A.

So, with -pr, a repair runs only for:
[A, B, C]

 > I could run nodetool repair on just 2 nodes(RF=3) instead of using 
nodetool repair –pr???

Yes.

You need to run two repairs on A and D.

 > What is the advantage of –pr then?

Whenever you want to minimize rapair impacts.

For example, suppose you got one node down for a while, and bring it 
back to the cluster.

You need to run rapair without affecting the entire cluster. Then, -pr 
is the option.

Thanks,
Takenori

(2013/03/01 7:39), Hiller, Dean wrote:
> Isn't it true if I have 6 nodes, I could run nodetool repair on just 2 nodes(RF=3) instead
of using nodetool repair –pr???
>
> What is the advantage of –pr then?
>
> I mean a repair involves all three nodes and pushes and pulls data, right?
>
> Thanks,
> Dean


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