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From Yan Chunlu <>
Subject Re: Moving to a new cluster
Date Thu, 22 Sep 2011 15:04:24 GMT
hi Aaron:

could you explain more about the issue about repair make space usage going

I am planning to upgrade my cluster from 0.7.4 to 0.8.6, which is because
the repair never works on 0.7.4 for me.
more specifically,
 and CASSANDRA-2156 <>.

from your description, I really worried about 0.8.6 might make it worse...


On Thu, Sep 22, 2011 at 7:25 AM, aaron morton <>wrote:

> How much data is on the nodes in cluster 1 and how much disk space on
> cluster 2 ? Be aware that Cassandra 0.8 has an issue where repair can go
> crazy and use a lot of space.
> If you are not regularly running repair I would also repair before the
> move.
> The repair after the copy is a good idea but should technically not be
> necessary. If you can practice the move watch the repair to see if much is
> transferred (check the logs). There is always a small transfer, but if you
> see data been transferred for several minutes I would investigate.
> When you start a repair it will repair will the other nodes it replicates
> data with. So you only need to run it every RF nodes. Start it one one,
> watch the logs to see who it talks to and then start it on the first node it
> does not talk to. And so on.
> Add a snapshot before the clean (repair will also snapshot before it runs)
> Scrub is not needed unless you are migrating or you have file errors.
> If your cluster is online, consider running the clean every RFth node
> rather than all at once (e.g. 1,4, 7, 10 then 2,5,8,11). It will have less
> impact on clients.
> Cheers
>  -----------------
> Aaron Morton
> Freelance Cassandra Developer
> @aaronmorton
> On 22/09/2011, at 10:27 AM, Philippe wrote:
> Hello,
> We're currently running on a 3-node RF=3 cluster. Now that we have a better
> grip on things, we want to replace it with a 12-node RF=3 cluster of
> "smaller" servers. So I wonder what the best way to move the data to the new
> cluster would be. I can afford to stop writing to the current cluster for
> whatever time is necessary. Has anyone written up something on this subject
> ?
> My plan is the following (nodes in cluster 1 are node1.1->1.3, nodes in
> cluster 2 are node2.1->2.12)
>    - stop writing to current cluster & drain it
>    - get a snapshot on each node
>    - Since it's RF=3, each node should have all the data, so assuming I
>    set the tokens correctly I would move the snapshot from node1.1 to node2.1,
>    2.2, 2.3 and 2.4 then node1.2->node2.5,2.6,2.,2.8, etc. This is because the
>    range for node1.1 is now spread across 2.1->2.4
>    - Run repair & clean & scrub on each node (more or less in //)
> What do you think ?
> Thanks

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