ScyllaDB Docs ScyllaDB Enterprise ScyllaDB for Administrators Procedures Cluster Management Procedures Create a ScyllaDB Cluster - Multi Data Centers (DC)

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Create a ScyllaDB Cluster - Multi Data Centers (DC)¶

Consult with the table below if each node in the cluster has internal IP for internal DC communication and external IP for cross DC communication.

Single Multi Data Centers Configuration Table¶

Parameter	Multi DC
seeds	External IP address
listen_address	Internal IP address
rpc_address	Internal IP address
broadcast_address	External IP address
broadcast_rpc_address	External IP address
endpoint_snitch	GossipingPropertyFileSnitch

Important

If the node has two physical network interfaces in a multi-datacenter installation:

Set listen_address to this node’s private IP or hostname.
Set broadcast_address to the second IP or hostname (for communication between data centers).
Set listen_on_broadcast_address to true.
Open the storage_port or ssl_storage_port on the public IP firewall.

Prerequisites¶

Make sure that all the ports are open.
Obtain the IP addresses of all nodes that have been created for the cluster.
Choose one of the nodes to be a seed node. You’ll need to provide the IP of that node using the seeds parameter in the scylla.yaml configuration file on each node.
Select a unique name as cluster_name for the cluster (identical for all the nodes in the cluster).
Choose which snitch to use (identical for all the nodes in the cluster). For a production system, it is recommended to use a DC-aware snitch, which can support the NetworkTopologyStrategy replication strategy for your keyspaces.

Decide the name of the rack, for example, RACK1, RACK2 or RC1, RC2.
Decide the name of the data center, for example, DC1, DC2 or US-DC, ASIA-DC.

Choose the data center name carefully. It is not possible to rename a data center later

When working with production environments, you must choose one of the snitches below:

Ec2multiregionsnitch - for AWS cloud-based, multi-data-center deployments.
GossipingPropertyFileSnitch - for bare metal and cloud (other than AWS) deployments.

Procedure¶

1. Install ScyllaDB on the nodes you want to add to the cluster. See Getting Started for further instructions, create as many nodes that you need. Follow the ScyllaDB install procedure up to scylla.yaml configuration phase.

In case that your node starts during the process follow these instructions

2. On each node, edit the scylla.yaml file to configure the parameters listed below. The file can be found under /etc/scylla/.

cluster_name - Set the selected cluster_name
seeds - Specify the IP of the node you chose to be a seed node. New nodes will use the IP of this seed node to connect to the cluster and learn the cluster topology and state.
listen_address - IP address that the ScyllaDB use to connect to other ScyllaDB nodes in the cluster
endpoint_snitch - Set the selected snitch
rpc_address - Address for CQL client connection

3. In the cassandra-rackdc.properties file, edit the rack and data center information. The file can be found under /etc/scylla/.

To save bandwidth, add the prefer_local=true parameter. ScyllaDB will use the node private (local) IP address when the nodes are in the same data center.

Start the nodes.

sudo systemctl start scylla-server

docker exec -it some-scylla supervisorctl start scylla

(with some-scylla container already running)

5. Verify that the nodes have been added to the cluster using nodetool status.

For Example:

In this example, we will show how to install a nine nodes cluster.

Install nine ScyllaDB nodes, three nodes in each data center (U.S, ASIA, EUROPE). The IP’s are:

U.S Data-center
Node# Private IP    Public IP
Node1 192.168.1.201 54.187.36.59 (seed)
Node2 192.168.1.202 54.187.142.201
Node3 192.168.1.203 54.187.168.20

ASIA Data-center
Node# Private IP    Public IP
Node4 192.168.1.204 54.191.72.56
Node5 192.168.1.205 54.187.25.99
Node6 192.168.1.206 54.191.2.121

EUROPE Data-center
Node# Private IP    Public IP
Node7 192.168.1.207 54.160.174.243
Node8 192.168.1.208 54.235.9.159
Node9 192.168.1.209 54.146.228.25

In each ScyllaDB node, edit the scylla.yaml file. See Single Multi Data Centers Configuration Table for reference.

U.S Data-center - 192.168.1.201

cluster_name: 'multi_dc_demo'
seeds: "54.187.36.59"
endpoint_snitch: GossipingPropertyFileSnitch
rpc_address: "192.168.1.201"
listen_address: "192.168.1.201"
broadcast_address: "54.187.36.59"
broadcast_rpc_address: "54.187.36.59"
listen_on_broadcast_address: true (optional)

ASIA Data-center - 192.168.1.204

cluster_name: 'multi_dc_demo'
seeds: "54.187.36.59"
endpoint_snitch: GossipingPropertyFileSnitch
rpc_address: "192.168.1.204"
listen_address: "192.168.1.204"
broadcast_address: "54.191.72.56"
broadcast_rpc_address: "54.191.72.56"
listen_on_broadcast_address: true (optional)

EUROPE Data-center - 192.168.1.207

cluster_name: 'multi_dc_demo'
seeds: "54.187.36.59"
endpoint_snitch: GossipingPropertyFileSnitch
rpc_address: "192.168.1.207"
listen_address: "192.168.1.207"
broadcast_address: "54.160.174.243"
broadcast_rpc_address: "54.160.174.243"
listen_on_broadcast_address: true (optional)

In each ScyllaDB node, edit the cassandra-rackdc.properties file with the relevant rack and data center information

Nodes 1-3

dc=US-DC
rack=RACK1

Nodes 4-6

dc=ASIA-DC
rack=RACK1

Nodes 7-9

dc=EUROPE-DC
rack=RACK1

Start the nodes.

sudo systemctl start scylla-server

docker exec -it some-scylla supervisorctl start scylla

(with some-scylla container already running)

Verify that the nodes have been added to the cluster by using the nodetool status command.

nodetool status

Datacenter: US-DC
=========================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
--   Address         Load            Tokens  Owns            Host ID                                 Rack
UN   54.191.2.121    120.97 KB       256     ?               c84b80ea-cb60-422b-bc72-fa86ede4ac2e    RACK1
UN   54.191.72.56    109.54 KB       256     ?               129087eb-9aea-4af6-92c6-99fdadb39c33    RACK1
UN   54.187.25.99    104.94 KB       256     ?               0540c7d7-2622-4f1f-a3f0-acb39282e0fc    RACK1

Datacenter: ASIA-DC
=======================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
--   Address         Load            Tokens  Owns            Host ID                                 Rack
UN   54.160.174.243  109.54 KB       256     ?               c7686ffd-7a5b-4124-858e-df2e61130aaa    RACK1
UN   54.235.9.159    109.75 KB       256     ?               39798227-9f6f-4868-8193-08570856c09a    RACK1
UN   54.146.228.25   128.33 KB       256     ?               7a4957a1-9590-4434-9746-9c8a6f796a0c    RACK1

Datacenter: EUROPE-DC
=========================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
--   Address         Load            Tokens  Owns            Host ID                                 Rack
UN   54.187.36.59    114.35 KB       256     ?               4c3e1533-1b78-45bf-8bd4-818090f019ab    RACK1
UN   54.187.142.201  109.54 KB       256     ?               d99967d6-987c-4a54-829d-86d1b921470f    RACK1
UN   54.187.168.20   109.54 KB       256     ?               2329c2e0-64e1-41dc-8202-74403a40f851    RACK1

Preventing Quorum Loss¶

If your cluster is symmetrical, i.e., it has an even number of datacenters with the same number of nodes, consider adding an arbiter DC to mitigate the risk of losing a quorum at a minimum cost. See Preventing Quorum Loss in Symmetrical Multi-DC Clusters for details.

Create a ScyllaDB Cluster - Multi Data Centers (DC)¶

Single Multi Data Centers Configuration Table¶

Prerequisites¶

Procedure¶

Preventing Quorum Loss¶

See also:¶