Warning "No data can be migrated from the disk group, because it belongs to a host that is in maintenance mode." seen when attempting to delete vSAN disk or disk group after placing vSAN host into maintenance mode

Products

• VMware vSAN

Issue/Introduction

Symptoms:

• When a vSAN host containing a failed disk or disk group is already in maintenance mode, the following warning will appear when attempting to delete the disk or disk group:
  (vSphere Client > vSAN Cluster > Configure > vSAN - Disk Management > Select the host with the disk/disk group to be deleted > Select the disk/disk group to be deleted > Click "Remove"):
  
  "No data can be migrated from the disk group, because it belongs to a host that is in maintenance mode. If the disk group contains any data that has not been migrated, the data will be lost. Any inaccessible objects will be permanently lost. Non-compliant objects might trigger a rebuild."

• The above warning would also be seen when attempting to delete a disk or disk group which is not failed.

Environment

VMware vSAN 8.x

Cause

• This is expected behaviour as the vSAN host has been placed into maintenance mode and moved to a vSAN decommissioned state.

• In this state, no data from the host can be moved to the other host.

• Thus the warning states that if the disk or disk group is to be deleted, then the data held by it would not be migrated and deleted forever.

Resolution

• After entering the host into maintenance mode, it must be ensured that there are no inaccessible vSAN objects, because deleting the disk or disk group on the host which is in maintenance mode can potentially cause data loss.

• If the host was placed into maintenance mode using "Ensure accessibility" or "Full data migration", then this warning can be ignored and the disk or disk group can be deleted.

Additional Information

Place a Member of vSAN Cluster in Maintenance Mode

Alternatively, the disk or disk group on the host can be removed without placing the host into maintenance mode after performing data migration pre-check as per this document, Remove Disk Groups or Devices from vSAN. Placing the host into maintenance mode and performing this activity is a safer option.