Extending a VM disk on vSAN fails with error "Insufficient disk space on datastore 'vsanDatastore'. The disk extend operation failed: There is not enough space on the file system for the selected operation."

Products

• VMware vSAN

Issue/Introduction

Symptoms: 

• Encountering the following error when attempting to extend a VM disk:  
  "Insufficient disk space on datastore 'vsanDatastore'. The disk extend operation failed: There is not enough space on the file system for the selected operation."
   
• The issue persists even though free space is available on the datastore.
• This is a vSAN ROBO/Stretch cluster setup.

Environment

• vSAN 7.x
• vSAN 8.x

Cause

• The issue is caused by the vSAN witness being in network partition state.
• This is not considered a functional vSAN Cluster, and therefore, the Cluster is unable to provide enough free space to execute the VM disk expansion successfully.

 

Resolution

1. Fix the vSAN Witness Cluster partition issue by following the fix mentioned in  vSAN Witness appliance partitioned from the stretch cluster
2. Once the Witness node is back online, please proceed to expand the disk of the VM. 

Additional Information

vSAN Datastore has enough free space but cannot expand VM disk. Error thrown "Insufficient disk space on datastore 'vsanDatastore' .... "