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From Peter Schuller <peter.schul...@infidyne.com>
Subject Re: mysterious data disappearance - what happened?
Date Fri, 09 Sep 2011 23:47:44 GMT
> cluster name for both machines.  So in other words, if we want to launch two
> separate instances of cassandra and keep them separate, we must make sure
> each uses a different cluster name or else they will gang up into the same
> cluster?  But how do they even discover each other?  Can someone enlighten
> me please?  Thanks.

It is highly recommended to use distinct cluster names, in particular
because it can help avoid accidentally "merging" two independent
clusters.

As for how it happened: There is no magic discovery going on that
would pick IP:s at random, but one could certainly e.g. accidentally
configure the seed node on one to point to the other or some such.

(1) does nodetool -h localhost ring show an unexpected node?
(2) i'd suggest checking system.log on each node for the first
appearance (if any) of the "unexpected" ip address and correlate (by
time) with what happened on the other node (was it restarted at the
time for example, potentially wth a bad conf?)
(3) are these two single-instance cassandras that have never
participated in another cluster?

-- 
/ Peter Schuller (@scode on twitter)

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