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From huyle <hu...@springpartners.com>
Subject Re: Decommission a node causing high IO usage on 2 other nodes
Date Wed, 30 Nov 2011 04:10:09 GMT
Yes, we do have RF=3.  

That explains it all.  Thanks Peter!

Huy


Peter Schuller wrote
> 
>> What may be causing high IO wait on 2.new and 3.new?
> 
> Do you have RF=3?
> 
> The problem with 'nodetool ring' in terms of interpreting those '0%'
> is that it does not take RF and replication strategy into account. If
> you have RF=3, whatever data has its primary range assigned to node N
> will also be on N+1 and N+2. Additionally, whatever data has it's
> primary range assigned to N-1 and N-2 will also have a copy on N.
> 
> So despite all the old nodes showing up as 0% in nodetool ring, they
> are in fact responsible for data. And you would expect to see nodes
> N+2 and N-2 be the two "old" nodes affected by decommissioning node N.
> (Unless I'm tripping myself up somewhere now...)
> 
> -- 
> / Peter Schuller (@scode, http://worldmodscode.wordpress.com)
> 


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