The Hidden Pitfalls of Hyper-V Automatic Checkpoints: Disk Space Woes and How to Regain Control

The Hyper-V automatic checkpoints feature, introduced with Windows Server 2016 and Windows 10 version 1607, promised to simplify virtual machine (VM) management and enhance system reliability. While this feature offers undeniable benefits, it’s not without its drawbacks. In this article, we’ll explore the problems associated with automatic checkpoints, with a particular focus on disk space issues, and guide you through the process of disabling this feature when necessary.

The Double-Edged Sword of Automatic Checkpoints

Automatic checkpoints in Hyper-V were designed to create seamless, consistent backups of virtual machines without interrupting their operation. This feature leverages the backup technology built into the guest operating system, allowing for more reliable checkpoints compared to the older standard checkpoint method.

However, the convenience of automatic checkpoints comes at a cost. Let’s delve into some of the key issues.

1. Disk Space Consumption

The most significant problem with automatic checkpoints is their voracious appetite for disk space. Each checkpoint creates a new differencing disk, which stores all changes made since the last checkpoint. Over time, these differencing disks can accumulate rapidly, especially on frequently used VMs or those with high write activity.

As these checkpoint files grow, they can quickly consume available disk space on the host system. This problem is exacerbated in environments with limited storage resources or when managing multiple VMs on a single host. In extreme cases, it can lead to the host running out of disk space, potentially causing system instability or VM crashes.

2. Performance Impact

While automatic checkpoints are designed to be less intrusive than their predecessors, they still have a performance impact. The creation and management of checkpoint files require system resources, which can affect the overall performance of both the host and the virtual machines, especially during peak usage periods.

3. Backup Complications

Ironically, a feature designed to enhance backup capabilities can sometimes complicate backup processes. Some backup solutions may struggle to handle the complex chain of differencing disks created by frequent automatic checkpoints, leading to longer backup times or even backup failures.

4. Management Overhead

With automatic checkpoints enabled, administrators may find themselves spending more time managing checkpoint files. This includes monitoring disk space usage, manually merging or deleting unnecessary checkpoints, and troubleshooting issues related to checkpoint proliferation.

5. Potential for Data Loss

In scenarios where disk space is exhausted due to unchecked checkpoint growth, there’s a risk of data loss. VMs may fail to write new data, or in worst-case scenarios, become corrupted and unbootable.

6. Licensing Considerations

For VMs running software with strict licensing requirements, frequent automatic checkpoints might inadvertently violate licensing terms by creating multiple “copies” of the software environment.

Regaining Control: How to Disable Hyper-V Automatic Checkpoints

Given these potential issues, some administrators may choose to disable automatic checkpoints. Here’s how you can do it:

For a Single VM:

1. Open Hyper-V Manager.
2. Right-click on the desired VM and select “Settings.”
3. In the left pane, click on “Management.”
4. Under “Checkpoints,” uncheck the box next to “Use automatic checkpoints.”
5. Click “Apply” and then “OK” to save the changes.

NOTE – if you uncheck the “Enable checkpoints” option at the top of the settings you will not be able to create manual checkpoints nor automatic checkpoints. However, since these options can be changed for a running VM, you may want to leave this option disabled to prevent accidental checkpoint creation. If you then later want to create a manual checkpoint, you can enable the option as necessary without rebooting the VM.

For Existing VMs (using PowerShell):

1. Open PowerShell as an administrator.
2. To disable automatic checkpoints for all existing VMs, run:
                  Get-VM | Set-VM -AutomaticCheckpointsEnabled $false

Conclusion

While automatic checkpoints in Hyper-V offer convenience and enhanced backup capabilities, they can lead to significant disk space issues and other complications if left unchecked. By understanding these potential problems and knowing how to disable the feature when necessary, administrators can maintain better control over their virtual environments.

Remember, disabling automatic checkpoints doesn’t mean abandoning the benefits of checkpointing altogether. Instead, it allows for a more deliberate and controlled approach to VM state management. As with many aspects of IT infrastructure, the key lies in finding the right balance between automation and manual control to suit your specific needs and resources.

Have any questions about how to disable Hyper-V automatic checkpoints? Please reach out to our IT and security experts at any time!