Redshift clusters should have Multi-AZ deployments enabled

How to fix it

Turn on Multi-AZ for the cluster, so its compute runs in two Availability Zones behind one endpoint. Three prerequisites gate it: an RA3 or RG node type, so a DC2 cluster has to be resized first; at least two nodes per zone; and a subnet group covering three Availability Zones, which is one more than Redshift.16 asks for. Compute roughly doubles, because the node count you specify is deployed in each zone.

In the console

Redshift → Clusters → the cluster → Edit → AZ configuration → Multi-AZ

With the AWS CLI

aws redshift modify-cluster --cluster-identifier <cluster-id> --multi-az --region <region>

With Terraform

resource "aws_redshift_cluster" "this" {
  cluster_identifier = var.cluster_identifier
  node_type          = var.node_type
  multi_az           = true
}