What type of disk is supported for OpenShift 4 control plane nodes in Azure?

Solution Verified - Updated

Environment

  • Red Hat OpenShift Container Platform (RHOCP)
    • 4
  • Azure Platform

Issue

  • What type of disk is supported for the control plane nodes in Azure?
  • Is Standard_LRS disk type supported for the control plane nodes?
  • What is the minimum disk type required to control plane?
  • How to extend the disk space after the cluster installation?

Resolution

The premium_LRS and standardSSD_LRS are supported for the control plane nodes in Azure. The standard_LRS is not supported for the control plane nodes due to the low performance.

While the minimum disk type required for the OpenShift 4 control plane in Azure is standardSSD_LRS, the default disk type is premium_LRS of 1TB, and specially recommended for clusters running production workloads. For additional information, refer to Why is the minimum recommended size of disk for control plane nodes 1024 GB when installing OpenShift 4 on Azure?.

By default, the storage comes from master nodes which should be enough since the workloads are running on the worker nodes. But to extend the OS disk size it would be needed to resize/replace the entire machine. Refer to Resizing Disks on Azure IPI Master Nodes in RHOCP 4 for additional information.

For additional Azure configuration parameters refer to the documentation: Installation configuration parameters for Azure.

Root Cause

The default disk type for the OpenShift 4 control plane in Azure is premium_LRS of 1 TB. standardSSD_LRS is also supported, but not recommended for production environments due to the performance required by the etcd. Refer to Azure Disk performance by region for additional information about the performance of P30 premium_LRS disks by region.

Diagnostic Steps

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On the Content from github.com is not included.installconfigs.install.openshift.io definition, check the following as the default disk type:

diskType:
  description: DiskType defines the type of disk. For control 
    plane nodes, the valid values are Premium_LRS and StandardSSD_LRS.
    Default is Premium_LRS.   
  enum:
  - Standard_LRS
  - Premium_LRS
  - StandardSSD_LRS
  type: string
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