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From srmore <comom...@gmail.com>
Subject Decommissioning a datacenter deletes the data (on decommissioned datacenter)
Date Thu, 07 Aug 2014 15:26:15 GMT
tl;dr: Decommissioning datacenters by running nodetool decommission on a
node deletes the data on the decommissioned node - is this expected ?

I am trying our some tests on my multi-datacenter setup. Somewhere in the
docs I read that decommissioning a node will stream its data to other nodes
but it still retains its copy of the data.

I was expecting the same behavior with multiple datacenters. I am using
cassandra 1.2.12. Following are my observations:


Lets say I have a datacenter DC1 which has keyspace "keyspace_dc_1" and I
have another datacenter DC2 which has keyspace "keyspace_dc_2". They
already have some data in them.

I add DC2 to DC1, update the replication factors on both the keyspaces.
Looking at the gossipinfo, I can see that the schemas are synced. I then
look at the cfstats output and I can see then both the keyspaces are
replicated on both the datacenters (also on the disk, as I can see a
non-zero sstable count).

Now, I decommission DC2:
1) Update the replication factors for the keyspaces.
2) Run nodetool decommission on all the nodes.

I see that I have lost all my keyspaces (and data), the keyspaces from DC1
and DC2. This does not seem normal to me, is this expected ?

Thanks,
Sandeep

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