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From Jeremiah Jordan <>
Subject Re: Adding a second datacenter
Date Mon, 05 Mar 2012 16:02:43 GMT
You need to make sure your clients are reading using LOCAL_* settings so 
that they don't try to get data from the other data center.  But you 
shouldn't get errors while replication_factor is 0.  Once you change the 
replication factor to 4, you should get missing data if you are using 
LOCAL_* for reading.

What version are you using?

See the IRC logs at the begining of this JIRA discussion thread for some 

But you should be able to:
1. Set dc2:0 in the replication_factor.
2. Set bootstrap to false on the new nodes.
2. Start all of the new nodes.
3. Change replication_factor to dc2:4
4. run repair on the nodes in dc2.

Once the repairs finish you should be able to start using DC2.  You are 
still going to need a bunch of extra space because the repair is going 
to get you a couple copies of the data.

Once 1.1 comes out it will have new nodetool commands for making this a 
little nicer per CASSANDRA-3483


On 03/05/2012 09:42 AM, David Koblas wrote:
> Everything that I've read about data centers focuses on setting things 
> up at the beginning of time.
> I've the the following situation:
> 10 machines in a datacenter (DC1), with replication factor of 2.
> I want to set up a second data center (DC2) with the following 
> configuration:
>   20 machines with a replication factor of 4
> What I've found is that if I initially start adding things, the first 
> machine to join the network attempts to replicate all of the data from 
> DC1 and fills up it's disk drive.  I've played with setting the 
> storage_options to have a replication factor of 0, then I can bring up 
> all 20 machines in DC2 but then start getting a huge number of read 
> errors from read on DC1.
> Is there a simple cookbook on how to add a second DC?  I'm currently 
> trying to set the replication factor to 1 and do a repair, but that 
> doesn't feel like the right approach.
> Thanks,

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