Why can’t I perform elastic resize for my Amazon Redshift cluster?

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I tried to use AWS CloudFormation for my Amazon Redshift cluster to perform an elastic resize. However, it performed a classic resize instead.

Resolution

Important: If you used the Amazon Redshift console to resize the cluster, then the cluster isn't registered in the AWS CloudFormation template. Instead, use the AWS CloudFormation template to be sure that the numberofNodes parameter is updated. Otherwise, Amazon Redshift might perform a classic resize, despite the cluster meeting the resize requirements. Amazon Redshift behaves this way when there are no changes to the node count since the last resize.

Amazon Redshift performs a classic resize when any of these requirements aren't met:

  • Only the numberofNodes parameter is modified.
  • For dc2.large or ds2.xlarge node types: You can only double the node count or decrease the node count by half of the original cluster.
  • For dc2.8xlarge or ds2.8xlarge node types: You can resize up to two times the original node count, or resize down to half of the original node count. For example, you can resize a 16 node cluster to any size that is between 8 and 32 nodes.
  • For ra3.16xlarge or ra3.4xlarge node types: You can resize up to four times the original node count, or resize down to one quarter of the original node count. For example, you can resize a 16 node cluster to any size that is between 4 and 64 nodes.
  • For ra3.xlplus node types: You can resize up to two times the original node count, or resize down to one quarter of the original node count. For example, you can resize a 16 node cluster to any size that is between 4 and 32 nodes.
  • The number of nodes can't exceed the number of slices. The number of slices are determined when the Amazon Redshift cluster is launched. For example, if you launch a cluster with two dc2.large nodes, then there are four slices of the cluster. This means that you can increase your node count only to four nodes when using elastic resize.

If your Amazon Redshift cluster performed a classic resize, then be sure to review the following areas:

  • Check the Amazon Redshift console to confirm the actual number of nodes in your cluster. Verify that it matches the numberofNodes parameter in your AWS CloudFormation template.
  • Use the DescribeClusters API to retrieve information from AWS CloudTrail and determine root cause analysis. Look for the elasticResizeNumberOfNodeOptions parameter in the AWS CloudTrail logs to verify whether your Amazon Redshift cluster is eligible for an elastic resize. The parameter doesn't list an option to update node count when the cluster slices fail to meet the elastic resize requirements.

Note: Before you update the node count for your Amazon Redshift cluster, use the DescribeNodeConfigurationOptions API. The DescribeNodeConfigurationOptions API can help you determine the appropriate node configurations for an elastic resize, such as the node count and type.

Related information

How do I resize an Amazon Redshift cluster?

Overview of managing clusters in Amazon Redshift

AWS OFFICIAL
AWS OFFICIALUpdated a month ago
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