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From Peter Schuller <peter.schul...@infidyne.com>
Subject Re: Decommission a node causing high IO usage on 2 other nodes
Date Wed, 30 Nov 2011 01:24:02 GMT
> 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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