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RE: [EXTERNAL] Cluster is unbalanced

Are you using any rack aware topology? What are your partition keys? Is it possible that your partition keys do not divide up as cleanly as you would like across the cluster because the data is not evenly distributed (by partition key)?



Sean Durity

lord of the (C*) rings (Staff Systems Engineer – Cassandra)

MTC 2250

#cassandra - for the latest news and updates


From: learner dba <cassandradba@xxxxxxxxx.INVALID>
Sent: Monday, June 18, 2018 2:06 PM
To: User cassandra.apache.org <user@xxxxxxxxxxxxxxxxxxxx>
Subject: [EXTERNAL] Cluster is unbalanced




Data volume varies a lot in our two DC cluster:

 Load       Tokens       Owns  

 20.01 GiB  256          ?     

 65.32 GiB  256          ?     

 60.09 GiB  256          ?     

 46.95 GiB  256          ?     

 50.73 GiB  256          ?     




 Load       Tokens       Owns  

 25.19 GiB  256          ?     

 30.26 GiB  256          ?     

 9.82 GiB   256          ?     

 20.54 GiB  256          ?     

 9.7 GiB    256          ?     


I ran clearsnapshot, garbagecollect and cleanup, but it increased the size on heavier nodes instead of decreasing. Based on nodetool cfstats, I can see partition keys on each node varies a lot:


Number of partitions (estimate): 3142552

Number of partitions (estimate): 15625442

Number of partitions (estimate): 15244021

Number of partitions (estimate): 9592992

Number of partitions (estimate): 15839280


How can I diagnose this imbalance further?