Change the Default Replication Factor
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To create a cluster with a replication factor (RF) that varies from the default of
3, follow this procedure. It guides you through adjusting the
allocate_tokens_for_local_replication_factor setting in the MissionControlCluster manifest. DataStax Mission Control does not recompute the token ranges and change tokens when modifying an existing cluster.
This example involves a 10-node datacenter and the need to create a DSE cluster with a RF of
Review the sample MissionControlCluster manifest:
apiVersion: missioncontrol.datastax.com/v1beta1 kind: MissionControlCluster metadata: name: demo spec: k8ssandra: cassandra: serverVersion: 6.8.25 config: cassandraYaml: num_tokens: 1 allocate_tokens_for_local_replication_factor: 5 datacenters: - metadata: name: dc1 size: 10
dc1is defined with
allocate_tokens_for_local_replication_factorsetting specifies a replication factor of
5, overriding the DataStax Mission Control default setting of
3. When you create a cluster, DataStax Mission Control computes and assigns tokens for the first
5nodes in the cluster, leaving the remaining
5nodes to determine their best tokens. DataStax Mission Control does not recompute token ranges or modify tokens for existing clusters.
Review the DSE Cluster token ring details with this command run from a node in a pod:
kubectl exec demo-dc1-rack1-sts-0 -c cassandra -- nodetool -u demo-superuser -pw <omitted> ring ks1
ks1is the last parameter, avoiding the resulting
Ownscolumn from displaying incongruous data.
Datacenter: dc1 ========== Address Rack Status State Load Owns Token 8301034833169298226 10.100.18.24 default Up Normal 78.88 KiB 50.00% -9223372036854775808 10.100.22.6 default Up Normal 78.89 KiB 60.00% -5534023222112865485 10.100.6.16 default Up Normal 68.74 KiB 50.00% -3689348814741910324 10.100.20.9 default Up Normal 73.65 KiB 50.00% -1844674407370955162 10.100.10.20 default Up Normal 68.74 KiB 50.00% -922337203685477582 10.100.0.17 default Up Normal 68.72 KiB 50.00% -1 10.100.19.6 default Up Normal 73.65 KiB 40.00% 1844674407370955161 10.100.8.16 default Up Normal 73.65 KiB 50.00% 5534023222112865484 10.100.23.6 default Up Normal 73.65 KiB 50.00% 7378697629483820645 10.100.5.19 default Up Normal 73.89 KiB 50.00% 8301034833169298226
Ownscolumn indicates that each node holds between 40% and 60% of the data. While not ideal this is still acceptable because the expected ownership for each node is calculated at 50% = 5 * 1/10. That is the RF multiplied by the num_tokens/node.
Rebalance an existing cluster. Assign tokens to new nodes that are joining an existing cluster.