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From Ananth Gundabattula <agundabatt...@threatmetrix.com>
Subject Re: Migrating data from 2 node cluster to a 3 node cluster
Date Tue, 09 Jul 2013 07:36:57 GMT
Hello everybody,

The thread below makes me wonder "Does RF matter when using sstable loader.?"  My assumption
was that stable loader will take care of RF when the streaming is done but just wanted to
cross check. We are currently moving data from a RF=1 to RF=3 cluster by using sstable loader
tool. We will of course be running repair on the destination nodes but was wondering how is
the following issue resolved using a repair if my understanding is wrong?

If the above assumption is wrong and since we are using Sstableloader which streams relevant
parts to of each table to the destination cluster, it means the destination folder will only
get one copy only (because origin RF =1 ) ? If that is the case, how will a repair resolve
when a data chunk from an empty folder is used as the chosen replica to perform repair  (
as it possible that  two "nearest neighbors" are empty in the first place ) .

Regards,
Ananth



From: aaron morton <aaron@thelastpickle.com<mailto:aaron@thelastpickle.com>>
Reply-To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <user@cassandra.apache.org<mailto:user@cassandra.apache.org>>
Date: Tuesday, July 9, 2013 3:24 PM
To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <user@cassandra.apache.org<mailto:user@cassandra.apache.org>>
Subject: Re: Migrating data from 2 node cluster to a 3 node cluster

Without vnodes the initial_token is stored in the yaml file, as well as the system LocationInfo
CF.

With vnodes the only place the tokens are stored is in the system KS. So moving a node without
it's system KS will cause it to generate new ones which will mean data is moved around.

Cheers

-----------------
Aaron Morton
Freelance Cassandra Consultant
New Zealand

@aaronmorton
http://www.thelastpickle.com

On 9/07/2013, at 11:23 AM, sankalp kohli <kohlisankalp@gmail.com<mailto:kohlisankalp@gmail.com>>
wrote:

"Leaving the system keyspaces behind is OK if you are not using vnodes. "

Why is it different for vnodes?


On Mon, Jul 8, 2013 at 3:37 PM, aaron morton <aaron@thelastpickle.com<mailto:aaron@thelastpickle.com>>
wrote:
This might work for user created keyspaces but might not work for system keyspace
Leaving the system keyspaces behind is OK if you are not using vnodes.

Cheers

-----------------
Aaron Morton
Freelance Cassandra Consultant
New Zealand

@aaronmorton
http://www.thelastpickle.com<http://www.thelastpickle.com/>

On 9/07/2013, at 10:03 AM, sankalp kohli <kohlisankalp@gmail.com<mailto:kohlisankalp@gmail.com>>
wrote:

"If RF=N or RF>N, you can just copy all SStables to all nodes, watching out for name collision."

This might work for user created keyspaces but might not work for system keyspace


On Mon, Jul 8, 2013 at 2:07 PM, Robert Coli <rcoli@eventbrite.com<mailto:rcoli@eventbrite.com>>
wrote:
On Fri, Jul 5, 2013 at 7:54 PM, srmore <comomore@gmail.com<mailto:comomore@gmail.com>>
wrote:
RF of old and new cluster is the same RF=3. Keyspaces and schema info is also same.

You have a cluster where RF=3 and N=2? Does it.. work?

What are the tokens of old and new nodes?
tokens for old cluster ( 2-node )

If RF=N or RF>N, you can just copy all SStables to all nodes, watching out for name collision.

=Rob






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