How to Add a "Compute Only" Node to a vSAN OSA Cluster

Products

• VMware vSAN 7.x
• VMware vSAN 8.x

Issue/Introduction

This article provides procedures and technical requirements for adding a compute-only node (ESXi host with no local storage) to an existing vSAN OSA cluster. This configuration is supported but requires specific environment considerations to ensure stability.

• Cluster Asymmetry: While supported, minimize significant levels of asymmetry within the cluster to prevent uneven performance and availability issues during host failure scenarios.
• Networking Requirements: Compute-only nodes must be configured with a vSAN VMkernel interface to communicate with storage nodes over the vSAN network.
• SDDC Manager (VCF Environments): Adding diskless hosts may trigger a "zero SSD devices" validation error. This requires a configuration bypass in the application.properties file of the Domain Manager.

Note:

• Broadcom does not recommend having unbalanced cluster configurations, and thus minimize significant levels of asymmetry.  This will help prevent potential availability and capacity issues during failure conditions, and minimize deviation in performance

        For more information please check:  Asymmetrical vSAN Clusters - What is Allowed, and What is Smart

• This article is not related to vSAN remote datastore mount or to HCI Mesh Architecture 

Environment

VMware vSAN 7.x

VMware vSAN 8.x

Resolution

1. Add the ESXi host to the vSAN Cluster on the vCenter server.
2. Add the ESXi host to the distributed virtual switch (dvSwitch) and migrate the Management Network.
3. Create a dedicated VMkernel Port for vSAN on the new host to ensure connectivity to storage nodes.

Additional Information

• Asymmetrical vSAN Clusters - What is Allowed, and What is Smart
• Add a Host to the vSAN Cluster