Imagine booting your virtual machine only to see a terrifying message — “Cannot open the disk VMDK … file is corrupted.”
A corrupt VMDK (Virtual Machine Disk) can instantly render your entire VMware virtual machine inaccessible, putting critical files, databases, and systems at risk. Since the VMDK contains everything from your operating system to user data, even a small corruption can disrupt an entire environment.
This article explains how to fix a corrupted VMDK file safely, step by step, without losing valuable data. You’ll learn what causes VMDK corruption, how to identify the issue, and proven methods to repair or recover your virtual disk using both VMware tools and trusted third-party utilities.
Understanding What a VMDK File Is
A VMDK (Virtual Machine Disk) is VMware’s proprietary virtual hard drive format that acts just like a physical disk inside a virtual machine. It contains everything needed for the VM to operate — from the operating system and installed applications to user data and configuration files. This format is used across VMware platforms, including Workstation, ESXi, and vSphere, allowing virtual machines to function independently of the underlying hardware.
There are several types of VMDK files depending on how data is stored and managed. A monolithic VMDK stores everything in one large file, while split disks break the data into 2 GB segments for easier storage. Some configurations use a descriptor + flat file system, where the descriptor holds metadata and points to the main flat data file. Snapshot (delta) files record changes made after a snapshot, preserving the original disk state. However, corruption can occur for many reasons — sudden power failures, disk errors, interrupted snapshots, or manual file edits — all of which can make the VMDK unreadable if not handled carefully.
Symptoms and Signs of a Corrupt VMDK
Error Messages You Might See
When corruption occurs, VMware typically throws one of these errors:
- “Cannot open the disk ‘.vmdk’ or one of the snapshot disks it depends on.”
- “The parent virtual disk has been modified since the child was created.”
- “File not found: .vmdk.”
- “Failed to lock the file.”
Behavioral Symptoms
Beyond these messages, you may also notice:
- The virtual machine fails to boot or hangs during startup.
- One or more virtual disks appear missing or inaccessible.
- Snapshot operations fail (cannot create, delete, or merge).
- Unexpected shutdowns or significant performance degradation.
Preliminary Checks Before Repair
Before attempting any repair, it’s crucial to perform a few safety checks to prevent further data loss. Start by creating a full backup or clone of your virtual machine. You can use VMware’s built-in Clone feature to duplicate the VM or simply copy the entire folder containing the .vmdk, .vmx, and .nvram files to a secure location. This ensures that even if the repair process fails or worsens the damage, you still have a recoverable version of your virtual machine.
Next, verify the VMDK file structure and the health of your storage. Make sure both the descriptor (.vmdk) and flat (.vmdk-flat) files are present and properly linked — mismatched or missing references are a common cause of corruption errors. Also, confirm that your physical storage is functioning correctly. Run SMART diagnostics on local drives, check the RAID or NAS status, and ensure your ESXi datastore isn’t showing I/O or read/write errors. These checks can help you identify whether the problem lies within the virtual disk itself or the underlying hardware.
Methods to Fix a Corrupt VMDK File
1. Repair the VMDK Descriptor File
When to use: The descriptor (.vmdk) file is missing or corrupted.
Steps:
- Open a healthy VM’s descriptor in a text editor (like Notepad++) as a reference.
- Recreate missing fields such as RW, CID, and parentCID.
- Ensure the “Extent Description” line correctly points to the .vmdk-flat file.
- Save the file with the original name and test the VM boot.
If successful, the VM should now recognize its data disk.
2. Use VMware Workstation’s Built-in Tools
VMware includes a command-line utility to check and repair VMDK files:
vmware-vdiskmanager -R “path\to\disk.vmdk”
What it does:
- Scans for inconsistencies and logical corruption within the virtual disk.
- Repairs metadata errors automatically.
Example output:
“Repairing virtual disk… done.”
If the repair completes successfully, try launching the VM again.
3. Recover from a Snapshot or Backup
If the corruption affects snapshot chains:
- Identify the latest delta file (-000001.vmdk, etc.).
- Check its descriptor for a valid parent reference.
- Correct broken links if needed.
- Consolidate snapshots or restore the VM from the most recent backup (using Veeam, Acronis, or vSphere Replication).
Snapshots can be powerful recovery points — but if mismanaged, they can also become a source of corruption.
4. Extract Data with Third-Party Software
If VMware utilities fail, use a professional VMDK recovery tool to extract files directly:
- DiskInternals VMFS Recovery – Designed for reading VMware ESXi volumes and recovering corrupted VMDK files.
- Stellar Data Recovery Technician – Recovers data from damaged or deleted virtual disks.
- UFS Explorer Professional Recovery – Ideal for reconstructing lost or corrupted VMDK and RAID environments.
These tools can mount a corrupted VMDK as a readable virtual disk, allowing you to browse and export recovered files safely.
5. Convert the VMDK to a New Virtual Disk
If the disk structure is too damaged for direct repair, clone it into a new one:
vmware-vdiskmanager -r source.vmdk -t 0 target.vmdk
This command creates a new, clean VMDK image using the readable portions of the original. It’s one of the safest ways to recover data without modifying the damaged file.
Advanced Scenarios
In more complex cases, restore vmdk from flat file can be challenging, especially with corrupted snapshots or ESXi-based disks. If the .vmdk-flat file is damaged, recovery may require specialized tools like R-Studio or DiskInternals VMFS Recovery to extract readable data or perform a sector-by-sector recovery to salvage remaining files.
When snapshots are corrupted, it’s important to identify and remove broken delta descriptors, then carefully merge parent and child disks using VMware command-line utilities — always creating a backup beforehand to avoid breaking the snapshot chain.
For ESXi servers, you can connect to the datastore via SSH and use the built-in repair command vmkfstools -x repair disk.vmdk, ensuring proper permissions and paths are set. This command directly repairs virtual disks within VMware’s native VMFS environment, often restoring functionality without external tools.
How to Prevent Future VMDK Corruption
Preventing future VMDK corruption starts with maintaining a reliable backup strategy. Automate daily or weekly backups using tools like vSphere Replication or Veeam, and always keep at least one off-site or cloud-based copy to ensure recoverability in case of failure. Avoid manually editing or renaming .vmdk or .vmx files, as small errors can render the entire virtual disk unusable — rely instead on VMware’s official utilities for all operations.
Regularly monitor hardware health through SMART diagnostics, and replace aging or unstable drives before they cause data loss. Finally, make it a habit to shut down virtual machines properly. Abrupt power-offs can corrupt disk writes, so using a UPS (Uninterruptible Power Supply) for physical hosts is essential to protect your VMware environment from unexpected outages.
Conclusion
A corrupted VMDK doesn’t always spell disaster. By following structured recovery steps — from verifying file integrity to using VMware repair utilities or specialized recovery software — you can often restore access to your virtual machine and recover every critical file.
Always keep regular backups, avoid risky manual file edits, and use VMware’s built-in tools for all disk management tasks. With careful maintenance and reliable recovery practices, your VMware environment can remain both resilient and data-safe.
