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From Andreas Finke <>
Subject Unbalanced ring with C* 2.0.3 and vnodes after adding additional nodes
Date Thu, 12 Dec 2013 10:49:46 GMT

after adding 2 more nodes to a 4 nodes cluster (before) we are experiencing high load on both
new nodes. After doing some investigation we found out the following:

- High cpu load on vm5+6
- Higher data load on vm5+6
- Write requests are evenly distributed to all 6 nodes by our client application (opscenter
-> metrics -> WriteRequests)
- Local writes are as twice as much in vm5 +6 (vm1-4: ~2800/s, vm5-6: ~6800/s)
- Nodetool output:

UN  vm1  9.51 GB    256     20,7%  13fa7bb7-19cb-44f5-af83-71a72e04993a  X1

UN  vm2  9.41 GB    256     20,0%  b71c2d3d-4721-4dde-a418-802f1af4b7a1  D1

UN  vm3  9.37 GB    256     18,9%  8ce4c419-d79c-4ef1-b3fd-8936bff3e44f  X1

UN  vm4  9.23 GB    256     19,5%  17974f20-5756-4eba-a377-52feed3a1b10  D1

UN  vm5  15.95 GB   256     10,7%  0c6db9ea-4c60-43f6-a12e-51a7d76f8e80  X1

UN  vm6  14.86 GB   256     10,2%  f64d1909-dd96-442b-b602-efee29eee0a0  D1

Although the ownership is lower on vm5-6 (which already is not right) the data load is way

Some cluster facts:

Node: 4 CPU, 6 GB RAM, virtual appliance

Cassandra: 3 GB Heap, vnodes 256

Schema: Replication strategy network, RF:2

Has anyone an idea what could be the cause for the unbalancing. Maybe we forgot necessary
actions during or after cluster expanding process. We are open for every idea.



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