You add the nodes with rf=0 so there’s no streaming, then bump it to rf=1 and 
run repair, then rf=2 and run repair, then rf=3 and run repair, then you either 
change the app to use local quorum in the new dc, or reverse the process by 
decreasing the rf in the original dc by 1 at a time

-- 
Jeff Jirsa


> On Feb 20, 2018, at 8:51 PM, Kyrylo Lebediev <kyrylo_lebed...@epam.com> wrote:
> 
> I'd say, "add new DC, then remove old DC" approach is more risky especially 
> if they use QUORUM CL (in this case they will need to change CL to 
> LOCAL_QUORUM, otherwise they'll run into a lot of blocking read repairs).
> Also, if there is a chance to get rid of streaming, it worth doing as usually 
> direct data copy (not by means of C*) is more effective and less troublesome.
> 
> Regards,
> Kyrill
> 
> ________________________________________
> From: Nitan Kainth <nitankai...@gmail.com>
> Sent: Wednesday, February 21, 2018 1:04:05 AM
> To: user@cassandra.apache.org
> Subject: Re: Best approach to Replace existing 8 smaller nodes in production 
> cluster with New 8 nodes that are bigger in capacity, without a downtime
> 
> You can also create a new DC and then terminate old one.
> 
> Sent from my iPhone
> 
>> On Feb 20, 2018, at 2:49 PM, Kyrylo Lebediev <kyrylo_lebed...@epam.com> 
>> wrote:
>> 
>> Hi,
>> Consider using this approach, replacing nodes one by one: 
>> https://mrcalonso.com/2016/01/26/cassandra-instantaneous-in-place-node-replacement/
>> 
>> Regards,
>> Kyrill
>> 
>> ________________________________________
>> From: Leena Ghatpande <lghatpa...@hotmail.com>
>> Sent: Tuesday, February 20, 2018 10:24:24 PM
>> To: user@cassandra.apache.org
>> Subject: Best approach to Replace existing 8 smaller nodes in production 
>> cluster with New 8 nodes that are bigger in capacity, without a downtime
>> 
>> Best approach to replace existing 8 smaller 8 nodes in production cluster 
>> with New 8 nodes that are bigger in capacity without a downtime
>> 
>> We have 4 nodes each in 2 DC, and we want to replace these 8 nodes with new 
>> 8 nodes that are bigger in capacity in terms of RAM,CPU and Diskspace 
>> without a downtime.
>> The RF is set to 3 currently, and we have 2 large tables with upto 70Million 
>> rows
>> 
>> What would be the best approach to implement this
>>    - Add 1 New Node and Decomission 1 Old node at a time?
>>    - Add all New nodes to the cluster, and then decommission old nodes ?
>>        If we do this, can we still keep the RF=3 while we have 16 nodes at a 
>> point in the cluster before we start decommissioning?
>>   - How long do we wait in between adding a Node or decomissiing to ensure 
>> the process is complete before we proceed?
>>   - Any tool that we can use to monitor if the add/decomission node is done 
>> before we proceed to next
>> 
>> Any other suggestion?
>> 
>> 
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