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Multi-AZ Deployment

CelerData supports Multiple Availability Zone (Multi-AZ) deployment for elastic clusters, providing enhanced availability and durability for your applications.

Overview​

When Multi-AZ deployment is enabled for an elastic cluster, at least three Coordinator Nodes will be deployed across three AZs to ensure the high availability of the metadata service. They are automatically balanced across the specified AZs. In the event of a failure in one of the AZs, automatic failover is performed to guarantee the continuity of service in the other two AZs.

On the other hand, the Multi-AZ deployment for warehouses in the cluster supports two policies of node distribution: Crossing AZ Policy and Single AZ Policy (Coming soon).

  • With Crossing AZ Policy selected, Compute Nodes within a warehouse are even distributed across three AZs. If an AZ experiences a failure, Compute Nodes in the remaining two AZs continue to provide services. You can simply scale out the Compute Nodes in the warehouse to compensate for the compute resource loss due to the AZ failure.
  • With Single AZ Policy selected, all Compute Nodes within a warehouse are deployed in the primary AZ of the three. In the event of a failure in AZ where the warehouse is located, you will need to manually transfer the warehouse to another AZ.

Deployment process with Multi-AZ​

Multi-AZ deployment is supported only for elastic CelerData clusters. And you can enable this feature only when deploying a cluster via Manual deployment. Currently, enabling Multi-AZ deployment via CloudFormation is not supported.

Multi-AZ-Elastic

In STEP1 of the deployment wizard, turn on the switch of Multiple availability zone and select the Coordinator Node count in the Cluster basic configuration section, and select a Node Distribution Policy for default_warehouse in the Initial warehouse section.

Multi-AZ-Step1

In STEP3 of the deployment wizard, you must specify three subnets in the Network configuration. Each of the subnet must be under an independent AZ, and they must all be either private subnets or public subnets under the same VPC. For more information, see Network configuration.

Multi-AZ-Step3

For detailed instructions of cluster deployment, see Deployment on AWS.

Network configuration with Multi-AZ​

While creating a network configuration for elastic clusters with Multi-AZ deployment enabled, you must specify three subnets for it. Each of the subnet must be under an independent AZ, and they must all be either private subnets or public subnets under the same VPC. For detailed instructions on creating network configurations, see Manage network configurations for AWS.

Multi-AZ-Network configuration

To create three AZs for the VPC of your network configuration, you must choose 3 in the field Number of Availability Zones on the VPC settings page when you creating the VPC and related resources.

Multi-AZ-Create VPC

Failover with Multi-AZ​

Warehouses with Crossing AZ Policy​

Because Compute Nodes of a warehouse with Crossing AZ Policy enabled are distributed across three AZs, the remaining two AZs will continue to provide services if one AZ fails. In this case, you only need to scale the warehouse out to compensate for the compute resource loss. For detailed instructions, see Scale an elastic cluster.

Warehouses with Single AZ Policy​

With Single AZ Policy enabled, Compute Nodes of the warehouse are deployed in the in the primary AZ of the three. If the primary AZ fails, you must manually transfer the warehouse to another subnet.

Follow these steps:

  1. Sign in to the CelerData Cloud BYOC console.

  2. On the Clusters page, click the cluster for which you want to transfer the warehouse.

  3. On the cluster details page, click Manage and choose Edit cluster.

    NOTE

    You can only transfer warehouses for clusters that are in the Running state. If a cluster is in not in the Running state, the Edit cluster menu item is disabled.

  4. On the page that appears, select the warehouse that you want to transfer from the Warehouse drop-down list in the Configure the node distribution section, select an available subnet to which you want to transfer the warehouse to, and then click Apply.

  5. In the message that appears, click Apply to apply the changes.

    The cluster enters the Updating state.

    When the operation is complete, the cluster returns to the Running state.

WARNING

Changing the primary subnet for warehouses with Single AZ Policy enabled will cause the Compute Nodes within to be re-deployed. Therefore, the services running on the Compute Nodes will be interrupted. Please operate with caution.

Change Node Distribution Policy​

You can change the Node Distribution Policy for an existing warehouse.

Follow these steps:

  1. Sign in to the CelerData Cloud BYOC console.

  2. On the Clusters page, click the cluster which contains the warehouse that you want to change the Node Distribution Policy for.

  3. On the cluster details page, click Manage and choose Edit cluster.

    NOTE

    You can only change the Node Distribution Policy for warehouses in clusters that are in the Running state. If a cluster is in not in the Running state, the Edit cluster menu item is disabled.

  4. On the page that appears, select the warehouse that you want to change the policy from the Warehouse drop-down list in the Configure the node distribution section, select a new policy from the Node distribution policy drop-down list, and then click Apply.

  5. In the message that appears, click Apply to apply the changes.

    The cluster enters the Updating state.

    When the operation is complete, the cluster returns to the Running state.

WARNING

Changing the Node Distribution Policy for warehouses may cause some Compute Nodes within to be re-deployed. Therefore, the services running on the Compute Nodes will be interrupted. Please operate with caution.