Provisioned space discrepancy and snapshot descriptor issues on vSAN ESA - VMware vSAN

Products

• VMware vSAN

Issue/Introduction

Symptoms

• VM Provisioned Space in vSphere UI is significantly higher (2x or more) than the disk size set in VM Edit Settings.
• VM directory contains snapshot-style disks (e.g., VMNAME-000001.vmdk) but no snapshots are visible in the Snapshot Manager.
• objtool listSnapshot returns 0 snapshots for the object.

Environment

VMware vSAN ESA 8.x

Cause

1. RAID Overhead: On vSAN ESA, RAID-5 (Erasure Coding) typically adds a 1.33x multiplier. Additionally, vSAN LFS (Log-structured File System) adds ~13.1% overhead.
2. Auxiliary Files: Provisioned space includes the PSF (Persistent State File), vSwp (Swap), and RAID overhead for all components.
3. Snapshot Inconsistency: Snapshot disks may remain in the directory due to failed consolidation or third-party backup processes, even if the Snapshot Manager database does not reflect them.

Resolution

Step 1: Validate Storage Calculation
Verify the provisioned space using the following formula for vSAN ESA: Total = (Disk Size * RAID Multiplier * 1.131) + Swap + PSF For RAID-5, use a multiplier of 1.33.

Step 2: Clear Inconsistent Snapshots
If snapshot disks exist without entries in vCenter:

1. Create a new manual snapshot of the affected VM.
2. Select Delete All Snapshots to trigger a full consolidation of the disk chain.
3, Verify the disk descriptor file updates to the base disk.

For more information on overheads, refer to  Storage space utilization calculator