Single data center deployment

A deployment scenario with a mixed workload cluster has only one data center for each type of workload.

In this scenario, a mixed workload cluster has only one data center for each type of node. For example, if the cluster has 3 Hadoop nodes, 3 Cassandra nodes, and 2 Solr nodes, the cluster has 3 data centers, one for each type of node. In contrast, a multiple data center cluster has more than one data center for each type of node.

In single data center deployments, data replicates across the data centers automatically and transparently. No ETL work is necessary to move data between different systems or servers. You can configure the number of copies of the data in each data center and Cassandra handles the rest, replicating the data for you.

To configure a multiple data center cluster, see Multiple data center deployment.


  • DataStax Enterprise is installed on each node.
  • Choose a name for the cluster.
  • For a mixed-workload cluster, determine the purpose of each node.
  • Get the IP address of each node.
  • Determine which nodes are seed nodes. (Seed nodes provide the means for all the nodes to find each other and learn the topology of the ring.)
  • Other possible configuration settings are described in the cassandra.yaml configuration file.
  • Set virtual nodes correctly for the type of data center. DataStax recommends using virtual nodes only on data centers running Cassandra real-time workloads. See Virtual nodes.


This configuration example describes installing a 6 node cluster spanning 2 racks in a single data center. The default consistency level is QUORUM.

  1. Suppose the nodes have the following IPs and one node per rack will serve as a seed:
    • node0 (Cassandra seed)
    • node1 (Cassandra)
    • node2 (Cassandra)
    • node3 (Analytics seed)
    • node4 (Analytics)
    • node5 (Analytics)
    • node6 (Search - seed nodes are not required for Solr.)
    • node7 (Search)
  2. If the nodes are behind a firewall, open the required ports for internal/external communication. See Configuring firewall port access.
  3. If DataStax Enterprise is running, stop the nodes and clear the data:
    • Packaged installs:
      $ sudo service dse stop
      $ sudo rm -rf /var/lib/cassandra/* ## Clears the data from the  default directories
    • Tarball installs:

      From the install directory:

      $ sudo bin/dse cassandra-stop
      $ sudo rm -rf /var/lib/cassandra/* ## Clears the data from the default directories
      Note: If you are clearing data from an AMI installation for restart, you need to preserve the log files.
  4. Set the properties in the cassandra.yaml file for each node.
    Important: After making any changes in the cassandra.yaml file, you must restart the node for the changes to take effect.
    • Packaged installs: /etc/dse/cassandra/cassandra.yaml
    • Tarball installs: install_location/resources/cassandra/conf/cassandra.yaml

    Properties to set:

    Note: If the nodes in the cluster are identical in terms of disk layout, shared libraries, and so on, you can use the same copy of the cassandra.yaml file on all of them.
    • num_tokens: 256 for Cassandra nodes
    • num_tokens: 1 for Hadoop and Solr nodes
    • -seeds: internal_IP_address of each seed node
    • listen_address: empty

      If not set, Cassandra asks the system for the local address, the one associated with its hostname. In some cases Cassandra doesn't produce the correct address and you must specify the listen_address.

    • auto_bootstrap: false (Add this setting only when initializing a fresh cluster with no data.)
    • If you are using a cassandra.yaml from a previous version, remove the following options, as they are no longer supported by DataStax Enterprise:
      ## Replication strategy to use for the auth keyspace.
      auth_replication_strategy: org.apache.cassandra.locator.SimpleStrategy
          replication_factor: 1


    cluster_name: 'MyDemoCluster'
    num_tokens: 256
      - class_name: org.apache.cassandra.locator.SimpleSeedProvider
             - seeds: ","
  5. After you have installed and configured DataStax Enterprise on all nodes, start the seed nodes one at a time, and then start the rest of the nodes:
    Note: If the node has restarted because of automatic restart, you must stop the node and clear the data directories, as described above.
  6. Check that your cluster is up and running:
    • Packaged installs: $ nodetool status
    • Tarball installs: $ install_location/bin/nodetool status