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From Zhu Han <schumi....@gmail.com>
Subject Re: Moving to a new cluster
Date Fri, 23 Sep 2011 01:43:53 GMT
On Thu, Sep 22, 2011 at 11:04 PM, Yan Chunlu <springrider@gmail.com> wrote:

>
> hi Aaron:
>
> could you explain more about the issue about repair make space usage going
> crazy?
>

I guess repair defers the compaction progress as it brings a lot of load.
For update-heavy workload, the space usage goes higher and higher during
repair.



>
> 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, CASSANDRA-2280<https://issues.apache.org/jira/browse/CASSANDRA-2280>
>  and CASSANDRA-2156 <https://issues.apache.org/jira/browse/CASSANDRA-2156>
> .
>
>
> from your description, I really worried about 0.8.6 might make it worse...
>
> thanks!
>
> On Thu, Sep 22, 2011 at 7:25 AM, aaron morton <aaron@thelastpickle.com>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
>> http://www.thelastpickle.com
>>
>> 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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