Failed to delete the snapshot due to high datastore usage. Error massage: There is no more space for virtual disk XXX.vmdk. You might be able to continue this session by freeing disk space on the relevant volume, and clicking Retry...

Products

• VMware vSAN

Issue/Introduction

Symptoms : 

• Unable to powered on the virtual machine in vSAN cluster.  
• In the summary of the virtual machine in vCenter UI there is an error message similar to:

The operation cannot be allowed at the current time because the virtual machine has a question pending: 'msg.hbacommon.outofspace: There is no more space for virtual disk 'PMC.XXXX-000001.vmdk'. You might be able to continue this session by freeing disk space on the relevant volume, and clicking Retry. Click Cancel to terminate this session.'

Environment

VMware vSAN 7.x
VMware vSAN 8.x

Cause

Snapshot consolidation may fail if the underline vSAN disk backing the virtual machine’s VMDK becomes nearly full, leaving insufficient space for operations such as snapshot merge, delete, or consolidation.

vSAN requires free space on the disk to perform these operations. When space is not available, the system will block further I/O to prevent data corruption.

In the observed scenario, automatic rebalancing was disabled, which prevented vSAN from redistributing data to less utilized disks in the cluster. As a result, the snapshot consolidation failed due to a lack of available space on the specific disk hosting the virtual disk object.

Resolution

To resolve the snapshot consolidation failure caused by disk space exhaustion in a vSAN environment, follow the steps below:

1. Enable Automatic Rebalancing

   • Ensure Automatic Rebalancing is enabled in the vSAN cluster. This feature helps maintain even data distribution across all disks, reducing the risk of individual disks becoming full.

   • Refer documentation on vSAN Proactive Rebalance and Automatic Rebalance for detailed guidance.

   • Note: VMware introduced Automatic Rebalancing in vSAN 6.7 Update 3 with the intention of gradually rolling it out across customer environments. As of vSAN 7.x, this feature remains disabled by default in many deployments. However, due to significant improvements in the resynchronization scheduler in later versions, VMware recommends enabling this feature in most production environments. There may be rare scenarios where temporary disabling is appropriate—such as when adding a large number of hosts at once or working in nested lab environments. For all other cases, Automatic Rebalancing should be kept enabled.

2. Verify per Disk Utilization in vSAN cluster:

   • Use the following command to check disk usage across all hosts in the vSAN cluster:

     cmmds-tool find -t HOSTNAME -f json | egrep "uuid|hostname" | sed -e 's/\"content\"://g' | awk '{print $2}' | sed -e 's/[\",\},\,]//g' | xargs -n 2 | while read hostuuid hostname; do echo -e "\n\nHost Name: $hostname::: Host UUID: $hostuuid\n Disk Name\t\t| Disk UUID\t\t| Disk Usage     | Disk Capacity | Usage Percentage" ; cmmds-tool find -f python -t DISK -o $hostuuid | grep uuid | cut -c 13-48 | while read diskuuid; do cmmds-tool find -f json -t DISK -o $hostuuid -u $diskuuid | egrep "uuid|content" | sed -e 's/\"content\":|\\"uuid\"://g' | sed -e 's/[\",\},\]//g' | awk '{printf $0}' | sed -e 's/},/\n/g' | awk '{print $37 " " $5 " " $45}' | while read disknaa diskcap maxcomp; do diskcapused=$(cmmds-tool find -f json -t DISK_STATUS -u $diskuuid | grep content | sed -e 's/[\",\},\]//g' | awk '{print $3}'); diskperc=$(echo "$diskcapused $diskcap" | awk '{print $1/$2*100}'); if [ "$maxcomp" != 0 ]; then echo -en " $disknaa\t| $diskuuid\t| $diskcapused\t | $diskcap\t | $diskperc%\n"; fi; done; done; done

   • This will display usage per disk, helping you identify if any disk is critically full.

3. Take Action Based on Disk Usage, If all disks have sufficient free space, proceed with snapshot consolidation.

   • If any disk is close to full, take one of the following actions:

   • Add capacity to the vSAN datastore (e.g., by adding disks or disk groups).

   • Clean up unused files or stale snapshots to free up space

Additional Information

For guidance on vSAN capacity planning and datastore sizing, refer to the official VMware documentation:
Planning Capacity in vSAN