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From Enrico Cavallin <cavallin.enr...@gmail.com>
Subject Uneven token distribution with allocate_tokens_for_keyspace
Date Thu, 28 Nov 2019 15:08:21 GMT
Hi all,
I have an old datacenter with 4 nodes and 256 tokens each.
I am now starting a new datacenter with 3 nodes and num_token=4
and allocate_tokens_for_keyspace=myBiggestKeyspace in each node.
Both DCs run Cassandra 3.11.x.

myBiggestKeyspace has RF=3 in dcOld and RF=2 in dcNew. Now dcNew is very
unbalanced.
Also keyspaces with RF=2 in both DCs have the same problem.
Did I miss something or even with  allocate_tokens_for_keyspace I have
strong limitations with low num_token?
Any suggestions on how to mitigate it?

# nodetool status myBiggestKeyspace
Datacenter: dcOld
=======================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
--  Address   Load       Tokens       Owns (effective)  Host ID
                  Rack
UN  x.x.x.x  515.83 GiB  256          76.2%
fc462eb2-752f-4d26-aae3-84cb9c977b8a  rack1
UN  x.x.x.x  504.09 GiB  256          72.7%
d7af8685-ba95-4854-a220-bc52dc242e9c  rack1
UN  x.x.x.x  507.50 GiB  256          74.6%
b3a4d3d1-e87d-468b-a7d9-3c104e219536  rack1
UN  x.x.x.x  490.81 GiB  256          76.5%
41e80c5b-e4e3-46f6-a16f-c784c0132dbc  rack1

Datacenter: dcNew
==============
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
--  Address    Load       Tokens       Owns (effective)  Host ID
                     Rack
UN  x.x.x.x   145.47 KiB  4            56.3%
7d089351-077f-4c36-a2f5-007682f9c215  rack1
UN  x.x.x.x   122.51 KiB  4            55.5%
625dafcb-0822-4c8b-8551-5350c528907a  rack1
UN  x.x.x.x   127.53 KiB  4            88.2%
c64c0ce4-2f85-4323-b0ba-71d70b8e6fbf  rack1

Thanks,
-- ec

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