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From aaron morton <aa...@thelastpickle.com>
Subject Re: Update the Keyspace replication factor online
Date Wed, 13 Apr 2011 02:52:02 GMT
Are you changing the replication factor or moving nodes ? 

To change the RF you need to repair and then once all repairing is done run cleanup to remove
the hold data. 

You can move whole nodes by moving all their data with them, assigning a new ip, and updating
the topology file if used.  

Aaron

On 13 Apr 2011, at 07:56, Yudong Gao wrote:

> Hi,
> 
> What operations will be executed (and what is the associated overhead)
> when the Keyspace replication factor is changed online, in a
> multi-datacenter setup with NetworkTopologyStrategy?
> 
> I checked the wiki and the archive of the mailing list and find this,
> but it is not very complete.
> 
> http://wiki.apache.org/cassandra/Operations
> "
> Replication factor is not really intended to be changed in a live
> cluster either, but increasing it may be done if you (a) use
> ConsistencyLevel.QUORUM or ALL (depending on your existing replication
> factor) to make sure that a replica that actually has the data is
> consulted, (b) are willing to accept downtime while anti-entropy
> repair runs (see below), or (c) are willing to live with some clients
> potentially being told no data exists if they read from the new
> replica location(s) until repair is done.
> "
> 
> More specifically, in this scenario:
> 
> {DC1:1, DC2:1} -> {DC2:1, DC3:1}
> 
> 1. Can this be done online without shutting down the cluster? I
> thought there is an "update keyspace" command in the cassandra-cli.
> 
> 2. If so, what operations will be executed? Will new replicas be
> created in new locations (in DC3) and existing replicas be deleted in
> old locations (in DC1)?
> 
> 3. Or they will be updated only with read with ConssitencyLevel.QUORUM
> or All, or "nodetool repair"?
> 
> Thanks!
> 
> Yudong


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