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From Konstantin Naryshkin <konstant...@a-bb.net>
Subject Changing the replication factor of a keyspace
Date Mon, 24 Oct 2011 16:43:45 GMT
We are setting up my application around Cassandra .8.0 (will move to
Cassandra 1.0 in the near future). In production the application will
be running in a two (or more) node cluster with RF 2. In development,
we do not always have 2 machines to test on, so we may have to run a
Cassandra cluster consisting of only a single node. In this case, we
have to reduce the RF of the column family to 1. We may need to switch
machines from one schema to the other and back again. This is not
something that will occur often and not in live production. I noticed
that there is an alter keyspace command in the cassandra-cli and
PyCassa, which should allow me to change the strategy options. So, it
is possible to switch a Cassandra instance from RF 1 to RF 2 and back
again? Will we have something horrible happen if we try to do it on a
node with data? Is there anything in particular that we have to do
before/after the transition to make the transition safe?

I assume that we have to first alter the keyspace and then
decommission one of the nodes and this will prevent us from losing
half of our data.

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