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Elastic resize in Amazon Redshift

by | Aug 6, 2021

Wondering how to perform elastic resize in Amazon Redshift? We can help you.

At Bobcares we assist our customers with several AWS queries as part of our AWS Support Services for AWS users, and online service providers.

Today, let us discuss how our Support Techs worked on this Redshift query.


How to perform elastic resize in Amazon Redshift?

Usually, Amazon Redshift allows you to migrate to a certain number of nodes during a cluster resize.

By default, Amazon Redshift aims to maintain the same number of slices in the target cluster.

With slice mapping, the time required to resize a cluster is reduced.

During the slice mapping process, Amazon Redshift reshuffles the cluster slices to the new compute nodes in your target cluster.

In order to, perform elastic resize you need to consider the following:

  • Elastic resize doesn’t sort tables or reclaim disk space. Run VACUUM to sort tables and reclaim disk space.
  • Next, elastic resize is only available for Amazon Redshift clusters that use the EC2-VPC platform.
  • Elastic resize operations often require less time to complete than classic resize operations.

Elastic resize operations don’t sort tables or reclaim disk space.

To compare, classic resize operations provision a new cluster while copying over data from your source cluster.

The classic resize operation then distributes the data to the new nodes according to distribution style, and runs the ANALYZE command to update this information.

As a result, it can take longer to perform a classic resize than an elastic resize on your Amazon Redshift cluster.

Today, let us see the steps followed by the Support Techs in order to perform this task.

How elastic resize works?

In Amazon Redshift, elastic resize can work differently depending on the target node type.

Firstly, check whether the target node type is the same as the source node type.

To check your node type, sign in to the Amazon Redshift console.

From the navigation menu, choose Clusters. The Clusters page indicates the node type under each cluster name.

Or, you can use the describe-clusters AWS Command Line Interface (AWS CLI) command to obtain more information about your Amazon Redshift cluster:

aws redshift describe-clusters --region <Cluster Region>


DC2 and DS2 node count limitations

If you perform an elastic resize on your Amazon Redshift cluster, note the following limitations for DC2 and DS2 node types:

  • For dc2.large or ds2.xlarge node types, use half or double the current number of nodes.
  • For dc2.8xlarge, ds2.8xlarge, ra3.4xlarge, or ra3.16xlarge node types, use half to double the current number of nodes.


Elastic resize best practices

Consider the following best practices when performing an elastic resize on your Amazon Redshift cluster:

  • Take a snapshot before you start the elastic resize process, especially if you are resizing a new cluster.
  • Then, use the describe-node-configuration-options AWS CLI command to get possible node configurations for a resize operation.
    Please note if you receive an error when running your AWS CLI command, be sure that you’re using the most recent version of the CLI.
  • VACUUM the cluster before resizing. Elastic resize doesn’t automatically delete rows that are marked for deletion.
  • Use the resize-cluster command to resize your cluster.


Some of the additional factors to consider


  • A cluster snapshot is required for an elastic resize. You can manage snapshots using the console or the Amazon Redshift CLI and API.
  • After you initiate an elastic resize operation in Amazon Redshift, the operation can’t be canceled. Wait until the resize operation completes before performing another resize operation or cluster reboot.
  • The new node configuration must have enough storage for existing data. Even when you add nodes, your new configuration might not have enough storage because of the way that the data is redistribute.
  • Performing an elastic resize on your Amazon Redshift cluster can cause data skew between nodes from an uneven distribution of slices. If you observe data skew in your Amazon Redshift cluster, perform a classic resize instead.
  • Perform a classic resize on your Amazon Redshift cluster if it’s the best option for your use case.


[Need help with the process? We’d be happy to assist]



In short, today we saw how our  Support Techs perform elastic resize in Amazon Redshift.


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