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From kurt Greaves <k...@instaclustr.com>
Subject Re: Streaming from 1 node only when adding a new DC
Date Tue, 14 Jun 2016 08:39:12 GMT
What version of Cassandra are you using? Also what command are you using to
run the rebuilds? Are you using vnodes?

On 13 June 2016 at 09:01, Fabien Rousseau <fabifabi95@gmail.com> wrote:

> Hello,
>
> We've tested adding a new DC from an existing DC having 3 nodes and RF=3
> (ie all nodes have all data).
> During the rebuild process, only one node of the first DC streamed data to
> the 3 nodes of the second DC.
>
> Our goal is to minimise the time it takes to rebuild a DC and would like
> to be able to stream from all nodes.
>
> Starting C* with debug logs, it appears that all nodes, when computing
> their "streaming plan" returns the same node for all ranges.
> This is probably because all nodes in DC2 have the same view of the ring.
>
> I understand that when bootstrapping a new node, it's preferable to stream
> from the node being replaced, but when rebuilding a new DC, it should
> probably select sources "randomly" (rather than always selecting the same
> source for a specific range).
> What do you think ?
>
> Best Regards,
> Fabien
>



-- 
Kurt Greaves
kurt@instaclustr.com
www.instaclustr.com

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