Mixing Hosts with Hybrid and All-Flash Disk Groups is not supported in vSAN

Products

• VMware vSAN

Issue/Introduction

Symptom:

It is not supported to mix hybrid and all flash hosts in a single vSAN cluster.

This type of configuration would cause multiple performance issues, due to some of the following reasons:

1. The Hosts with All-Flash Disk Groups would operate and perform at much higher speeds than Hosts with Hybrid Disk Groups. When the Hybrid Hosts are not able to function at the same speed, queuing issues can occur, which may lead to data inconsistency and potential congestion.
2. The mixed configuration complicates the operational aspects of vSAN, such as monitoring of disk space, balancing components, etc.

Environment

VMware vSphere ESXi 7.x

VMware vSphere ESXi 8.x

Resolution

• To have a consistent disk group configuration on all the vSAN nodes, follow below steps -

Note: Compare the disks utilized as HDD on vSAN node with hybrid configuration to other nodes to make sure the device is truly a SSD or not. Please proceed with the below steps only if the device was SSD since marking a HDD device as Flash/SSD will not increase the device's performance and may even lead to the performance related issues in the cluster. Below steps will help to configure all flash configuration on all the disk groups.

• • Place the vSAN node into maintenance mode.
  • Then remove the hybrid disk groups.
  • If the capacity devices have falsely been identified as HDD, then mark it as Flash by selecting vSAN node > Configure > Storage device > Select the capacity disk > Mark it as Flash.
  • Rescan storage from the cluster level.
  • Create the disk group again on the vSAN node.

Additional Information

For more information, see:

• vSAN Plan and Design