How to Start Recovering a VMFS Datastore After Corruption

A VMFS datastore forms the backbone of most VMware environments, storing virtual machines, applications, and critical business data. But when corruption occurs, the impact can be devastating—VMs may become inaccessible, downtime can stretch into hours or days, and the risk of permanent data loss looms.

The financial and operational cost of such incidents is significant. That’s why knowing the right first steps when faced with a corrupted VMFS datastore is crucial. Acting too quickly or without a plan often worsens the situation. This guide provides a structured approach to help administrators start recovery safely and effectively.

VMFS Explained and Why Corruption Happens

VMFS (VMware File System) is VMware’s clustered file system used in ESXi environments. It allows multiple ESXi hosts to access the same storage simultaneously, enabling features like vMotion, HA, and DRS. VMFS is optimized for concurrent read/write operations and large virtual machine disk (VMDK) files.

Common Causes of VMFS Corruption

Despite its reliability, VMFS can become corrupted due to multiple factors:

• Hardware issues – disk failures, RAID controller malfunctions, or bad sectors.
  
  
• Improper ESXi shutdowns or crashes – leaving incomplete writes on the datastore.
  
  
• RAID misconfiguration or rebuild errors – accidental overwriting of parity data.
  
  
• Sudden power loss – especially during intensive I/O operations.
  
  
• Human errors – accidental partition deletion, formatting, or mismanagement.
  
  
• Firmware or driver incompatibility – mismatched versions can corrupt metadata.
  
  

Understanding the cause helps shape the recovery strategy and prevent repeated failures.

Recognizing the Symptoms of VMFS Corruption

Detecting VMFS corruption isn’t always straightforward, but there are clear indicators administrators should watch for. A corrupted datastore may refuse to mount in vSphere or ESXi, and virtual machines can suddenly become inaccessible or appear as “orphaned.” You might also encounter errors such as “Cannot open the disk” or “File system not recognized.”

In some cases, partitions may look missing or unreadable when inspected through command-line tools, while performance issues like I/O errors, host freezes, or significant slowdowns can signal deeper damage. Recognizing these symptoms quickly is critical—early action often prevents the corruption from escalating and improves the chances of successful recovery.

Immediate Precautions Before Attempting Recovery

The wrong move at this stage can mean permanent data loss. To minimize risks:

• Stop all write operations immediately – continuing use may overwrite recoverable data.
  
  
• Document the environment – note VMFS version, ESXi build, RAID layout, and storage hardware details.
  
  
• Disconnect the datastore from production workloads to avoid accidental writes.
  
  
• Clone or image affected disks using tools like dd, Clonezilla, or enterprise-grade solutions.
  
  
• Work only on disk images – preserving original media ensures you always have a fallback.
  
  
• Avoid reformatting or reinitializing unless you’re absolutely sure it’s part of a recovery plan.
  
  

Initial Steps in VMFS Datastore Recovery

Step 1: Verify Hardware Health

Check the physical layer first. Review RAID controller logs, inspect SMART data for failing drives, and confirm RAID volume consistency. If hardware is unstable, no recovery method will hold.

Step 2: Confirm Storage Visibility in ESXi

Log in to the ESXi shell or use vSphere Client to check whether the device is detected.
 Run:

esxcli storage filesystem list

This shows available filesystems and their states.

Step 3: Attempt Manual Mount

If the datastore is visible but unmounted, try:

esxcli storage filesystem mount -l <datastore_name>

or mount using the datastore UUID.

Step 4: Check Partition Tables and Metadata

Use partedUtil to inspect partition tables or vmkfstools to validate VMFS metadata. Missing partitions often signal corruption.

Step 5: Use Recovery Tools if Mount Fails

• Built-in ESXi tools are limited, but worth trying.
  
  
• Third-party recovery solutions designed for VMFS can parse corrupted metadata and extract VMDK files directly from datastore images.

Recovery Strategies Depending on Scenario

The right recovery path depends on the nature of the corruption. If the issue stems from metadata corruption, specialized VMFS recovery tools can often rebuild or reconstruct damaged structures, making the recovering vmfs datastore readable again. When the problem involves a corrupted partition table, the focus should be on carefully restoring partitions without overwriting the underlying data blocks—working on disk images is strongly recommended to avoid irreversible mistakes.

In situations where only virtual machine files are damaged, it may still be possible to extract VMDK files directly from the datastore image and repair them individually. On the other hand, if the corruption originates from the RAID layer, that must be stabilized before touching the VMFS volume. Reconstructing the RAID array correctly is critical; attempting VMFS recovery on a degraded or unstable RAID can permanently compromise the data.

Best Practices to Minimize Future VMFS Corruption

Recovery is one side of the equation—prevention is the other. Adopt these practices:

• Maintain regular backups of VMFS datastores and critical VMs.
  
  
• Deploy UPS and power protection to prevent sudden outages.
  
  
• Keep firmware, drivers, and ESXi updated to avoid incompatibilities.
  
  
• Monitor and validate RAID health with proactive drive replacements.
  
  
• Implement snapshots and replication for disaster recovery readiness.

Key Takeaways

Recovering a VMFS datastore after corruption requires calm, methodical action. The temptation to rush into formatting or rebuilding can be costly. Instead, follow a structured process: stop writes, document your environment, create safe copies, and attempt recovery with the right tools.

The key takeaway: Always work on images, never the original data, and when in doubt, escalate to specialized recovery solutions or professionals. Taking disciplined steps early is often the difference between a successful recovery and permanent data loss.