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Last updated: May 06, 2024

Repairing and Recovering Corrupt VMDK Files

VMDK is one of the three most used virtual disk formats, and it comes out as the most preferred option for more people – also, it is the proprietary virtual disk format for VMware.

Although a virtual machine file, VMDK files can get corrupted just like local files saved on a hard disk, and when that happens, you either recover the good version of the VMDK file from a backup or use a third-party VMDK recovery program.

Well, in this article, we will explain the different ways you can recover a corrupt VMDK file in VMware environments. While these methods have worked for different people, be sure to make a full backup or take a snapshot of your VM before proceeding below.

Understanding VMDK File Corruption

A corrupt VMDK file could be the reason your VM is not powering on, or you cannot fully access the VM’s content. Hereunder are some common reasons why a VMDK file may be corrupt.

Causes for Corrupt VMDK File

Improper Shutdowns: If a virtual machine is not properly shut down, it can result in incomplete or corrupt data being written to the VMDK file.
Hardware Failures: Issues with underlying hardware, such as disk failures or problems with storage arrays, can corrupt the data stored in VMDK files.
Virus or Malware Attacks: Malicious software can corrupt or damage the contents of a VMDK file either by direct infection or by harming the system operations that affect file integrity.
Software Bugs or Glitches: Bugs in the virtual machine software or in the operating systems running within the VM can lead to file corruption.
Snapshot Complications: Mishandling snapshots, such as failing to properly merge them after restoration or deletion, can leave VMDK files in a corrupt state.

Other Causes for VMDK File Corruption

Network Failures: For configurations where VMDK files are stored on network-attached storage, interruptions or instability in the network can cause file corruption during read/write operations.
Power Failures: Sudden power losses while the VM is writing to the disk can corrupt the VMDK file, similar to improper shutdowns.
Incorrect Editing of VMDK Files: Manual edits to VMDK files, if not done properly, can corrupt the file structure.
Storage Space Issues: Running out of storage space while the VMDK file is being written or modified can lead to corruption.
Concurrent Access Issues: If multiple processes attempt to access the VMDK file simultaneously without proper locking mechanisms, it can lead to data corruption.

Methods of Repairing Corrupt VMDK Files

There are a few safe and recommendable ways to repair a corrupt VMDK file. Be sure to try out these procedures carefully.

Booting Methods

Repairing corrupt VMDK (Virtual Machine Disk) files can be crucial for recovering data and ensuring that virtual machines run smoothly. Here are some methods, focusing initially on booting methods, to help you restore a corrupted VMDK file:

1. Booting from an Alternative Medium

Use a Rescue Disk: Booting the virtual machine from a rescue disk or an installation media can help you access the underlying filesystem without the need to boot from the corrupted VMDK file. This method allows you to run diagnostic tools and perform repairs on the disk.

2. Using Bootable Recovery Tools

Third-party Tools: DiskInternals VMFS Recovery tool can be booted directly to analyze and repair VMDK files. These tools often come with more sophisticated features to handle various types of file system corruption.

3. Safe Mode Boot

Boot into Safe Mode: Depending on the operating system your VM is running, you might be able to boot into Safe Mode. This can be particularly useful if the corruption is caused by faulty system files or drivers, as Safe Mode loads only the essential components of the OS.

4. Host System Tools

Access via Host: If you are running a VM on a host system with VMware, you can sometimes repair the VMDK file using utilities available on the host, like vmkfstools. This tool can check the consistency of a VMFS volume and repair VMDK files.

5. VMware Recovery Options

VMware Snapshot Recovery: If snapshots of the VM are available, restoring to a previous snapshot can be a quick way to revert to a state before the corruption occurred.
VMware Converter: Another approach is to use VMware Converter to attempt to convert the VMDK to a new VM, which might bypass the corruption.

6. Manual Mount and Repair

Mount the VMDK Manually: Using tools like VMware Workstation or free utilities that can mount VMDK files, you can mount the corrupted disk on another virtual machine or physical computer to perform file recovery or disk repair.

7. File System-Specific Repair Tools

Using FSCK or CHKDSK: Depending on the file system used inside the VMDK (e.g., NTFS, ext4), you can use standard file system repair tools like fsck (for Linux) or chkdsk (for Windows) to try and repair the file system errors within the VMDK.

Command Line Solutions

When dealing with corrupt VMDK files, using command line solutions can often provide a powerful and direct approach to repair. Here's how you can use Command Prompt to address VMDK corruption:

Using Command Prompt on Windows

1. VMware Disk Mount Utility
- VMware provides a Disk Mount utility that allows you to mount a VMDK file as a drive. Once mounted, you can use standard Windows tools like chkdsk to attempt repairs.
- First, download and install the VMware Disk Mount Utility.
- Open Command Prompt as Administrator and mount the VMDK file:
  less
  vmware-mount[drive letter]: [path to VMDK file]
- Once mounted, use chkdsdk to repair the file system within the VMDK:
  bash
  chkdsk [mounted drive letter]: /f
2. Using VMware vmkfstools
- For users with access to a VMware ESXi host or a Linux system with vmkfstools installed, this tool can be very useful. It’s typically used on VMware ESX/ESXi servers but is also available on other platforms.
- Connect to the ESXi host via SSH or access the Linux terminal.
- Run the following command to check and repair the VMDK file:
  css
  vmkfstools -x check [path to VMDK file] vmkfstools -x repair [path to VMDK file]
- These commands check the consistency of the VMDK file and attempt to fix any detected issues.
3. FSCK for Linux File Systems
- If the VMDK contains a Linux file system, you can use fsck to check and repair file system errors.
- First, mount the VMDK using a loop device in a Linux environment:
  bash
  sudo losetup /dev/loop0 [path to VMDK file] sudo kpartx -a /dev/loop0 sudo fsck -y /dev/mapper/loop0p1
- Adjust /dev/loop0 and /dev/mapper/loop0p1 according to your loop device and partition mapping.
4. NTFSfix for NTFS File Systems
- If the file system within the VMDK is NTFS (commonly used in Windows environments), you can use ntfsfix available on Linux systems:
  css
  sudo ntfsfix [path to your NTFS partition]
- This command will attempt to repair the NTFS file system and is often used when NTFS volumes won't mount correctly because of session or corruption issues.

General Tips

Backup Before Repair: Always ensure you have backups of your VMDK files before attempting repairs, as some operations can potentially result in data loss.
Work in a Controlled Environment: Whenever possible, perform these operations in a test environment first to avoid any accidental data loss or further corruption.

Backup Solutions

Having a robust backup solution in place is often the most straightforward and safest method to recover from a corrupted VMDK file. Here's how you can handle a situation where you need to restore a corrupted VMDK file from a backup:

1. Verify Backup Integrity

Before proceeding with any restoration process, ensure that your backups are intact and free from errors. You can verify backup integrity using tools provided by your backup software, which often include verification checks to confirm that the stored data can be restored successfully.

2. Restoration Process

Using Backup Software: Most enterprise and many free backup solutions offer straightforward mechanisms to restore virtual machines or individual files from backups. Use the software’s management console to select the corrupted VMDK file and initiate a restore operation.
Manual Restore: If you handle backups manually (e.g., copying VMDK files to a backup server), you can manually copy the backup VMDK file to the original location. Ensure the virtual machine is powered off before you replace the VMDK file.

3. Using Snapshots

If you have VM snapshots (not to be confused with full backups), you can revert the VM to a previous state before the corruption occurred. This is done through the virtualization platform’s management interface, like VMware vSphere Client:
css
Right-click on VM -> Snapshot -> Revert to Latest Snapshot
Be aware that reverting to a snapshot can result in data loss for any changes made since the snapshot was taken.

4. Incremental and Differential Backups

If using incremental or differential backups, ensure that you restore the full backup first, then apply each incremental or differential backup in the order they were created. This sequence is crucial for maintaining the integrity of your data.

5. Testing Restored Data

After restoration, start the virtual machine using the restored VMDK file to ensure that the VM boots correctly and that all data is intact and operational.
It's a good practice to check the restored system’s logs and run any necessary diagnostic tools to confirm that everything is functioning as expected.

6. Automation and Regular Testing

Automate the backup process where possible, and regularly test backups by restoring VMs in a controlled environment. This ensures that your backup processes are always reliable and that your data can be restored when needed.

7. Cloud Backup Solutions

Consider using cloud-based backup solutions for added resilience. Cloud backups can provide scalable, secure, and off-site storage for your VMDK files, minimizing the risk of data loss due to physical damage at your primary site.

8. Documentation and Training

Document the backup and restoration procedures clearly, and ensure that your IT staff are trained in these procedures. This helps in reducing downtime and errors in an emergency when restoring data from backups.

Professional Software Solutions

Actually, there are quite a number of third-party software applications that support VMDK file format and allow you to repair them when corrupt. DiskInternals VMFS Recovery software is a reliable software program capable of repairing corrupt VMDK images.

The software supports many file systems, and RAID levels, too. It has a clear-cut interface that any user could easily understand. DiskInternals VMFS Recovery can fix corrupted VMware boot images, access your invisible ESX Server datastores, mount VMFS volumes, and read inaccessible VMFS datastores. More so, this software can connect to vSphere or ESXi/ESX servers to recover lost VMDK files.

Step One: Download and install DiskInternals VMFS Recovery on your Windows PC and launch it.
Step Two: Connect to your VMware server via SSH and mount the VMDK drive: on the DiskInternals home screen, click on “Drives” on the top menu and select Mount Image.
Step Four: You can now access the VMDK image file as a local drive. Launch the recovery wizard, select the corrupt VMDK file and choose Full Recovery mode for the best results.
Step Five: During the scan, DiskInternals VMFS Recovery will automatically repair the VMDK, read it, as well as examine for the VMFS datastores, volumes, and RAID (if used) connected to the file.
Step Six: After the scan, VMFS Recovery will display all recovered files (shown with a red asterisk). You can restore the recovered file(s) and your VMDK image will most likely be fixed.

Preventing data corruption and effectively troubleshooting corrupt VMDK files are essential aspects of managing VMware environments. Here's a guide to both prevent and troubleshoot VMDK data corruption:

Prevention of VMDK Data Corruption

Regular Backups and Snapshots
- Implement a rigorous backup regime that includes frequent backups and snapshots. Ensure backups are stored in multiple locations and tested regularly for integrity.
Avoid Abrupt Shutdowns
- Ensure virtual machines are properly shut down rather than abruptly turning off the VM or host. Use UPS (Uninterruptible Power Supplies) to prevent unexpected shutdowns due to power failures.
Disk Maintenance
- Regularly perform disk maintenance tasks such as defragmentation (for older file systems), checking for file system errors, and using built-in tools like VMware’s vmkfstools for VMFS volumes.
Monitor Disk Usage
- Avoid overfilling datastores. High disk utilization can lead to decreased performance and increased risk of file corruption. Monitor and maintain adequate free space on datastores.
Hardware Checks
- Regularly check and maintain hardware health. This includes storage arrays, RAID configurations, and network connections to prevent hardware-related corruption issues.
Use Redundant Storage
- Implement RAID configurations for redundancy to protect against disk failures and to ensure data integrity and availability.
Software and Firmware Updates
- Keep your VMware ESXi servers, guest operating systems, and all firmware up to date with the latest patches and security updates to protect against vulnerabilities that could lead to corruption.

Troubleshooting Corrupt VMDK Files in VMware

Identify the Extent of Corruption
- Start by identifying how widespread the corruption is. Is it affecting a single file, multiple files, or an entire datastore?
Check VMware Logs
- Review VMware ESXi logs and vmkernel logs for any error messages related to disk failures, file system errors, or I/O issues that can indicate what might have caused the corruption.
Verify VMFS Datastore Integrity
- Use vmkfstools to check the integrity of VMFS datastores. This tool can also be used to repair VMFS volumes, which can resolve underlying issues affecting VMDK files.
bash
vmkfstools -V
Attempt to Mount the VMDK Manually
- Try to attach the corrupt VMDK to a new VM as a secondary disk to see if it can be mounted. If it mounts, you may be able to recover data from it.
Use Third-Party Recovery Tools
- If built-in tools fail, consider using third-party recovery tools designed for VMDK files. These tools often have more sophisticated algorithms to recover data from corrupted files.
Restore from Backup
- If troubleshooting efforts fail, restore the VMDK file from a backup. If possible, restore to a test environment first to verify the integrity of the backup.
Consult VMware Support
- If the corruption issue is complex or critical, involving VMware support can provide additional expertise and tools to resolve the issue.

By adhering to best practices in VM and datastore management and by being prepared with effective troubleshooting steps, you can prevent most causes of VMDK corruption and handle incidents more effectively when they occur.

Tip: how to mount VMFS

Conclusion

In conclusion, dealing with VMDK files—whether preventing corruption, repairing them, or restoring data from backups—requires a multifaceted approach that balances proactive measures and responsive troubleshooting techniques.

Preventive strategies are foundational and involve regular and robust backup regimes, proper system shutdown procedures, diligent disk and hardware maintenance, and keeping software up-to-date. These steps help minimize the risk of corruption and ensure that your systems remain reliable and data integrity is maintained.

When it comes to repairing corrupt VMDK files, the use of command line tools like vmkfstools or third-party software can be instrumental. These tools offer capabilities to check, repair, and recover data from damaged VMDK files, providing a crucial line of defense against data loss.

In instances where VMDK files are beyond repair, having a strong backup solution in place is invaluable. Being able to restore from backups quickly and effectively not only mitigates the impact of corruption but also significantly reduces downtime and operational disruptions.

Lastly, in the face of actual data corruption, effective troubleshooting techniques are essential. These include examining VMware logs, verifying datastore integrity, and using advanced recovery tools or VMware support when necessary. Each step in the troubleshooting process is aimed at quickly identifying the problem, mitigating damage, and restoring functionality.

Overall, a comprehensive understanding and implementation of these practices ensure that virtual environments are robust, secure, and resilient against data corruption, thereby safeguarding critical information and maintaining business continuity.

FAQ

How do I recover a corrupt VMDK file?
Steps to Repair a Corrupted VMDK File:
- Open the VMDK File Recovery Tool.
- Select the corrupted VMDK file.
- Choose your scanning mode and set your preferences.
- Identify the volume you want to repair and adjust any custom settings.
- Choose your desired recovery mode.
- Begin the scanning process on the selected volume.
How to rebuild a VMDK?
If the VMDK descriptor is missing, you can easily recreate it by following these steps:
- Create a new virtual disk that matches the size of the one missing its descriptor.
- Open the newly created descriptor VMDK file in a text editor.
- Modify the line in the descriptor file that points to the -flat.vmdk file to match the path of the original -flat.vmdk.
- Save the changes, and then copy the modified descriptor file to replace the missing or corrupted descriptor file in the original location.
How do I clean up orphaned VMDK files?
To manage and remove orphaned VMDK files, follow these steps:
- Navigate to your management interface by clicking on My Dashboard > Virtualization > Sprawl.
- Find the section labeled Orphaned VMDKs to identify any VMDK files that are no longer associated with any VM.
- To delete the orphaned files, click on Delete datastore file for the appropriate vCenter, such as rio-vcenter.
- Confirm the deletion by clicking Delete.