Multiple data center deployment
A deployment scenario with a mixed workload cluster has more than one data center for each type of node.
In this scenario, a mixed workload cluster has more than one data center for each type of node. For example, if the cluster has 4 Hadoop nodes, 4 Cassandra nodes, and 2 Solr nodes, the cluster could have 5 data centers: 2 data centers for Hadoop nodes, 2 data centers for Cassandra nodes, and 1 data center for Solr nodes. A single data center cluster has only 1 data center for each type of node
To configure a single data center cluster, see Single data center deployment.
To configure a multi-node cluster with multiple data centers:
- 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.)
- Develop a naming convention for each data center and rack, for example: DC1, DC2 or 100, 200 and RAC1, RAC2 or R101, R102.
- 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 data centers. The default consistency level is QUORUM.
Suppose you install DataStax Enterprise on these nodes:
- node0 10.168.66.41 (seed1)
- node1 10.176.43.66
- node2 10.168.247.41
- node3 10.176.170.59 (seed2)
- node4 10.169.61.170
- node5 10.169.30.138
- If the nodes are behind a firewall, open the required ports for internal/external communication. See Configuring firewall port access.
If DataStax Enterprise is running, stop the nodes and clear the data:
$ 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 directoriesNote: If you are clearing data from an AMI installation for restart, you need to preserve the log files.
- Packaged installs:
Set the properties in the cassandra.yaml file for each
Important: After making any changes in the cassandra.yaml file, you must restart the node for the changes to take effect.Location:
- 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
## Replication strategy to use for the auth keyspace. auth_replication_strategy: org.apache.cassandra.locator.SimpleStrategy auth_replication_options: replication_factor: 1
You must include at least one seed node from each data center. It is a best practice to have more than one seed node per data center.
cluster_name: 'MyDemoCluster' num_tokens: 256 seed_provider: - class_name: org.apache.cassandra.locator.SimpleSeedProvider parameters: - seeds: "10.168.66.41,10.176.170.59" listen_address:
If necessary, change the dse.yaml file on each node to specify the
snitch to be delegated by the DseDelegateSnitch. For more information about
snitches, see the About Snitches.
- Packaged installs: /etc/dse/dse.yaml
- Tarball installs: install_location/resources/dse/conf/dse.yaml
Example of specifying the PropertyFileSnitch:
In the cassandra-topology.properties file, use your naming
convention to assign data center and rack names to the IP addresses of each
node, and assign a default data center name and rack name for unknown
- Packaged installs: /etc/dse/cassandra/cassandra-topology.properties
- Tarball installs: install_location
# Cassandra Node IP=Data Center:Rack 10.168.66.41=DC1:RAC1 10.176.43.66=DC2:RAC1 10.168.247.41=DC1:RAC1 10.176.170.59=DC2:RAC1 10.169.61.170=DC1:RAC1 10.169.30.138=DC2:RAC1 # default for unknown nodes default=DC1:RAC1
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.
- Packaged installs: See Starting DataStax Enterprise as a service.
- Tarball installs: See Starting DataStax Enterprise as a stand-alone process.
Check that your cluster is up and running:
- Packaged installs: $ nodetool status
- Tarball installs: $ install_location/bin/nodetool status