Migrate from Windows Server 2016 Hyper-V Cluster to Windows Server 2025 Hyper-V Cluster

Question

Hi

Is it possible to create a new Hyper-V cluster using three Windows Server 2025 servers and migrate virtual machines from an existing failover cluster of three Windows Server 2016 servers? What documentation or advice is available for this migration? Additionally, do the new 2025 servers need to join the domain/Active Directory?

Regarding the network configuration, the new servers have 2 gigabit NICs and 4 10G NICs. What is the recommended setup for these NICs across various roles, considering that two of the 10G NICs will be dedicated to storage/iSCSI, CSV, Live Migration, etc.?

Thanks!

• ron

Answer 1

Yep - that's possible, although there are a few considerations:

1. Migration feasibility:

You cannot add Windows Server 2025 nodes to an existing 2016 cluster, because mixed-mode clustering is not supported between these versions. Therefore:

• You must build a new cluster using Windows Server 2025.
• Then, you can migrate VMs from the 2016 cluster to the new one.

Supported Migration Methods:

• Export/Import VMs.
• Shared Nothing Live Migration (if both clusters are on the same domain and compatible network-wise).
• Storage Migration (if using SMB or cluster-shared volumes).

Microsoft generally recommends Shared Nothing Live Migration for minimal downtime if both clusters coexist temporarily.

2. Documentation & guidance:

Key resources:

• Microsoft Docs – Failover Clustering
• Hyper-V Live Migration Overview
• Windows Server In-Place Upgrade Paths

Additional Tips:

• Always validate the Failover Cluster configuration using Test-Cluster.
• Ensure identical VM generation, virtual switch names, and integration services.

3. Active Directory domain requirement:

You can use workgroup-based clusters, but keep in mind the following restrictions:

Workgroup Cluster Support

Feature	Supported in Workgroup Cluster?	Notes
Failover Clustering	Yes	Since Windows Server 2016
Hyper-V Role	Yes	Full support
Cluster Shared Volumes (CSV)	es	Supported with SMB or iSCSI
Live Migration	Limited	Only Credential Security Support Provider (CredSSP) — no Kerberos
Cluster-Aware Updating (CAU)	No	Not supported without AD
SMB Authentication	Limited	No Kerberos — use certificates or NTLM
Storage Spaces Direct (S2D)	No	Requires domain membership
Cluster Name Object in AD	No	Uses local authentication or DNS-based access
Management Tools (SCVMM, etc.)	Limited	Often assume domain membership

4. Recommended network configuration (6 NICs: 2x1G + 4x10G):

You can split NICs across roles for performance and isolation. Here's a recommended configuration:

Gigabit NICs (1G) – Management and Backup roles

NIC	Role	Notes
NIC1	Management OS	Join domain, RDP, DNS, etc.
NIC2	Backup / Out-of-band	Optional – can isolate backup traffic.

10G NICs – High-throughput roles

NIC	Role	Notes
NIC3	iSCSI/Storage	Dedicated to iSCSI (use MPIO). No teaming for iSCSI.
NIC4	iSCSI/Storage	Same as above. One NIC per path for redundancy.
NIC5	Live Migration	Enable SMB Direct (RDMA) if supported. Use compression or TCP if not.
NIC6	Cluster + CSV + Heartbeat	Enable cluster communication + CSV traffic. Tag appropriately via metrics.

💡 Note: You can adjust roles depending on your storage configuration (e.g., SMB vs iSCSI), but keep Live Migration and storage traffic on separate NICs. Avoid teaming unless for specific roles like Management or CSV/Live Migration when RDMA is unavailable.

You might want to also consider:

• Enable jumbo frames (MTU 9000) on 10G NICs if your switch infrastructure supports it.
• Keep DNS, Time Sync, and domain connectivity stable.
• Ensure cluster validation is 100% successful before bringing VMs in.

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hth

Marcin

Answer 2

Thanks Marcin

BTW, if we have a new replacement storage system (iSCSI-based cabinet), should I be using the Storage Spaces Direct to transfer the guest images over from the old storage?

-ron