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From Carlos Alonso <>
Subject Re: Migrating from single node to cluster
Date Fri, 26 Feb 2016 09:22:13 GMT
Hi Jason.

Moving from one node to two has exactly the same process as moving from 2
to 3 or any other +1 jump. Basically you configure the node and make it
join the ring and Cassandra will take care of assigning data and load to
that new node.

Regarding how much data your new node should have or how much data has been
moved across it all depends on the replication factor of your keyspaces.

The replication factor is basically the number of replicas your data will
have and that's configured per keyspace. It may happen that you keyspace is
configured with replication factor = 1 and therefore very few (or even no)
data was required to be moved from the first node to the second one.

About the percentages shown in nodetool status, have you provided a
keyspace as an argument? Nodetool status cannot determine the percentage of
owned data for the whole cluster. A keyspace has to be provided for that
(you probably saw a warning note at the last line of nodetool status'

Hope this helps.


Carlos Alonso | Software Engineer | @calonso <>

On 26 February 2016 at 03:53, Jason Kania <> wrote:

> Hi,
> I am wondering if there is any documentation on migrating from a single
> node cassandra instance to a multinode cluster? My searches have been
> unsuccessful so far and I have had no luck playing with tools due to terse
> output from the tools.
> I currently use a single node having data that must be retained and I want
> to add two nodes to create a cluster. I have tried to follow the
> instructions at the link below but it is unclear if it even works to go
> from 1 node to 2.
> Almost no data has been transferred across and nodetool status is showing
> that 0% of the data is owned by either node although I cannot determine
> what the percentages should be in the case that the configuration is
> intended for data redundancy.
> Datacenter: datacenter1
> =======================
> Status=Up/Down
> |/ State=Normal/Leaving/Joining/Moving
> --  Address       Load       Tokens       Owns (effective)  Host
> ID                               Rack
> UN  648.16 MB  256          0.0%
> 5ce4f8ff-3ba4-41b2-8fd5-7d00d98c415f  rack1
> UN  3.31 MB    256          0.0%
> b56f6d58-0f60-473f-b202-f43ecc7a83f5  rack1
> I also looked to see if there were any tools to check whether replication
> is in progress but had no luck.
> The second node is bootstrapped and nodetool repair indicates that nothing
> needs to be done.
> Any suggestions on a path to take? I am at a loss.
> Thanks,
> Jason

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