Multiple data center deployment per workload type
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 the Solr nodes. A single data-center cluster has only one data center for each type of node.
- Isolating replicas from external infrastructure failures, such as networking between data centers and power outages.
- Distributing data replication across multiple, geographically dispersed nodes.
- Between different locations in a physical data center.
- Between public cloud providers and on-premise managed data centers.
- Use separate physical or virtual data centers to prevent the slow down of a real-time analytics jobs by other analytics jobs on live data.
To configure a multi-node cluster with multiple data centers:
- A good understanding of how Cassandra works. Be sure to read at least Understanding the architecture, Data Replication, and Cassandra's rack feature.
- DataStax Enterprise is installed on each node.
- Choose a name for the cluster.
- For a mixed-workload cluster, determine the purpose of each node.
- Determine the snitch and replication strategy. The GossipingPropertyFileSnitch and NetworkTopologyStrategy are recommended for production environments.
- Get the IP address of each node.
- Determine which nodes are seed nodes. Do not make all nodes seed nodes. Please read Internode communications (gossip).
- 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 and property files such as cassandra-rackdc.properties.
- 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:
- Installer-Services and Package installations:
$ sudo service dse stop $ sudo rm -rf /var/lib/cassandra/* ## Clears the data from the default directories
- Installer-No Services and Tarball installations:
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.
- Installer-Services and Package installations:
Set the properties in the cassandra.yaml file for each
node, located in:
Important: After making any changes in the cassandra.yaml file, you must restart the node for the changes to take effect.
- Installer-Services and Package installations: /etc/dse/cassandra/cassandra.yaml
- Installer-No Services and Tarball installations: 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 host name. In some cases Cassandra doesn't produce the correct address and you must specify the listen_address.
- auto_bootstrap: false
Add the bootstrap setting only when initializing a fresh cluster with no data.
- endpoint_snitch: snitch
- 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:
cassandra-rackdc.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
- Installer-Services and Package installations: /etc/dse/cassandra
- Installer-No Services and Tarball installations: install_location/resources/cassandra/conf
# 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.
- Packages/Services: See Starting DataStax Enterprise as a service.
- Tarball/No Services: See Starting DataStax Enterprise as a stand-alone process.
Check that your cluster is up and running:
- Installer-Services and Package installations: $ nodetool status
- Installer-No Services and Tarball installations: $ install_location/bin/nodetool status
Datacenter: DC1 ======================= Status=Up/Down |/ State=Normal/Leaving/Joining/Moving -- Address Load Tokens Owns Host ID Rack UN 10.168.66.41 45.96 KB 256 27.4% c885aac7-f2c0-... RAC1 UN 10.168.247.41 66.34 KB 256 36.6% fa31416c-db22-... RAC1 UN 10.169.61.170 55.72 KB 256 33.0% f488367f-c14f-... RAC1 Datacenter: DC2 ======================= Status=Up/Down |/ State=Normal/Leaving/Joining/Moving -- Address Load Tokens Owns Host ID Rack UN 10.176.43.66 45.96 KB 256 27.4% f9fa31c7-f3c0-... RAC1 UN 10.176.170.59 66.34 KB 256 36.6% a5bb526c-db51-... RAC1 UN 10.169.30.138 55.72 KB 256 33.0% b836478f-c49f-... RAC1
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