How to Upgrade & Migrate Hyper-V VMs to Windows Server 2025
Windows Server 2025 has arrived, and if you’re managing Hyper-V virtual machines, you’re probably wondering about the best path forward. I’ve been working with virtualization environments for years, and I know that upgrading can feel daunting—but it doesn’t have to be.
In this comprehensive guide, I’ll walk you through everything you need to know about upgrading and migrating your Hyper-V VMs to Windows Server 2025. Whether you’re running a small lab or managing enterprise infrastructure, these proven methods will help you make the transition smoothly.
Why Upgrade to Windows Server 2025?
Before we dive into the technical steps, let’s talk about why you’d want to upgrade in the first place. Windows Server 2025 brings several compelling improvements to Hyper-V:
Enhanced security features including advanced firmware protections and better isolation capabilities. Improved performance with optimizations for modern hardware and faster VM provisioning. Better management tools that simplify day-to-day operations and troubleshooting.
The new version also extends support timelines, which matters if you’re planning long-term infrastructure investments.
Prerequisites: What You’ll Need
Getting prepared is half the battle. Here’s what you should have ready before starting:
Hardware requirements: Your physical server needs at least a 64-bit processor with Second Level Address Translation (SLAT) support, 4GB RAM minimum (though I recommend much more for production environments), and adequate storage space for your VMs plus the new OS.
Software requirements: Valid Windows Server 2025 licenses, current backups of all VMs (seriously, don’t skip this), and administrative access to your Hyper-V hosts.
Network preparation: Document your current network configuration, ensure you have a maintenance window scheduled, and notify users of potential downtime.
Method 1: In-Place Upgrade of the Hyper-V Host
This approach upgrades your existing Windows Server installation to 2025 while keeping your VMs intact. It’s the fastest method but comes with some risk.
Step 1: Backup Everything
I can’t stress this enough—back up your entire environment. Export all VMs to external storage, create system state backups of your host server, and document your current configuration including virtual switches, storage paths, and network settings.
Step 2: Run the Pre-Upgrade Health Check
Mount your Windows Server 2025 installation media and run the setup from within your current OS. Choose the option to check for compatibility issues without installing. Address any warnings or errors before proceeding.
Step 3: Perform the In-Place Upgrade
Launch the Windows Server 2025 setup and select “Upgrade: Install Windows and keep files, settings, and applications.” Follow the wizard prompts, which typically takes 30-60 minutes depending on your hardware. The server will restart multiple times during this process.
Step 4: Verify and Update
After the upgrade completes, check that all VMs appear in Hyper-V Manager. Install the latest Windows updates and verify all virtual switches and storage configurations are intact. Start your VMs one at a time and confirm they’re functioning properly.
Pro tip: I always start with a non-critical VM first to test the waters before bringing production systems back online.
Method 2: Side-by-Side Migration
This is my preferred method for production environments because it provides a clean slate and a rollback path.
Step 1: Prepare Your New Server
Install Windows Server 2025 on new hardware or a separate disk. Install the Hyper-V role using Server Manager or PowerShell with this command:
powershell
Install-WindowsFeature -Name Hyper-V -IncludeManagementTools -RestartConfigure your virtual switches to match your source server’s network topology.
Step 2: Export VMs from the Source Server
On your existing Hyper-V host, shut down each VM gracefully. In Hyper-V Manager, right-click each VM and select “Export.” Choose a destination path on shared storage or external media. The export process includes all virtual hard disks, checkpoints, and configuration files.
Step 3: Import VMs to Windows Server 2025
On your new Windows Server 2025 host, open Hyper-V Manager and click “Import Virtual Machine.” Browse to the exported VM folder and select the configuration file. Choose “Register the virtual machine in-place” if your storage is already accessible, or “Copy the virtual machine” if you’re moving it to new storage.
Step 4: Update VM Configuration Version
This is a critical step that many people miss. By default, imported VMs retain their original configuration version for compatibility. To take advantage of Windows Server 2025 features, you need to upgrade the VM configuration version.
First, shut down the VM completely. Then run this PowerShell command:
Update-VMVersion -Name "YourVMName"
Important warning: This operation is irreversible. Once you upgrade the configuration version, you cannot move that VM back to an older Hyper-V host.
Step 5: Test and Validate
Start each VM and verify functionality. Check network connectivity, application performance, and integration services. Monitor the VMs for at least 24 hours before decommissioning your old host.
Method 3: Live Migration (Zero-Downtime Approach)
If you have a Hyper-V cluster or two standalone hosts that can communicate, you can migrate VMs without shutting them down.
Prerequisites for Live Migration
Both servers must be in the same Active Directory domain (or configured for constrained delegation). Live Migration must be enabled on both hosts. Network connectivity between hosts should be solid—preferably a dedicated migration network.
Performing Live Migration
In Hyper-V Manager on your source server, right-click the running VM and select “Move.” Choose “Move the virtual machine” and select your Windows Server 2025 host as the destination. Choose whether to move storage as well or just the VM. The wizard handles the rest, typically completing in minutes for most VMs.
The VM continues running throughout this process. Users won’t notice anything except possibly a brief network blip.
Updating VM Integration Services
After migrating to Windows Server 2025, you’ll want to update Integration Services on your guest VMs. For Windows guests, this happens automatically through Windows Update once you upgrade the VM configuration version.
For Linux guests, you may need to update the Linux Integration Services manually depending on your distribution. Most modern Linux distros include these in the kernel.
Common Issues and Troubleshooting
Through countless migrations, I’ve encountered these issues repeatedly:
VM won’t start after migration: Usually a configuration version mismatch or missing virtual switch. Check that all virtual network adapters are connected to valid switches.
Poor performance after upgrade: Often related to outdated Integration Services or incorrect VM settings. Verify that Dynamic Memory and CPU settings are appropriate for your workload.
Storage path errors: These occur when imported VMs reference paths that don’t exist on the new host. You’ll need to update the VM configuration to point to correct storage locations.
Post-Migration Best Practices
Once you’ve successfully migrated, take these additional steps to optimize your environment:
Update all VM configuration versions to leverage new features. Review and optimize VM resource allocations—Windows Server 2025’s improved memory management might allow you to run more VMs per host. Implement regular backup schedules using Windows Server Backup or third-party tools. Document your new configuration thoroughly, including network topology, storage layout, and disaster recovery procedures.
Should You Upgrade the Configuration Version Immediately?
This is a question I get asked all the time. My answer: it depends on your situation.
If you’re running a mixed environment where you might need to move VMs back to older hosts, hold off on upgrading configuration versions. If you’re fully committed to Windows Server 2025 and want access to the latest features, upgrade the configuration versions after you’ve validated that everything works.
There’s no rush—VMs will continue running perfectly fine with older configuration versions.
Planning Your Migration Timeline
For a typical environment, here’s a realistic timeline:
Week 1: Planning, documentation, and backups. Week 2: Lab testing with non-production VMs. Week 3-4: Phased migration of production workloads. Week 5: Monitoring, optimization, and documentation updates.
Don’t try to rush this process. I’ve seen too many administrators create problems by migrating everything over a single weekend.
Final Thoughts
Upgrading to Windows Server 2025 is a significant step that brings real benefits to your virtualization infrastructure. The key to success is preparation, testing, and taking a methodical approach.
I’ve walked through these processes dozens of times across different environments, and the side-by-side migration method consistently delivers the best results for production systems. It gives you a clean installation, provides a fallback option, and lets you validate everything before committing fully.
- Design
