BLOG: Windows Server / Azure Local keeps setting Live Migration to 1 - here is why

Affected products:

Windows Server 2022, Windows Server 2025

Azure Local 21H2, Azure Local 22H2, Azure Local 23H2

Network ATC

 

Dear Community,

I have seen numerous reports from customers running Windows Server 2022 servers or Azure Local (Azure Stack HCI) that Live Migration settings are constantly changed to 1 per Hyper-V Host, as mirrored in PowerShell and Hyper-V Host Settings.

The customer previously set the value to 4 via PowerShell, so he could prove it was a different value at a certain time. 
First, I didn't step into intense research why the configuration altered over time, but the stumbled across it, quite accidently, when fetching all parameters of Get-Cluster.

According to an article a LCU back in September 2022 changed the default behaviour and allows to specify the live migrations at cluster level.

The new live migration default appears to be 1 at cluster level and this forces to change the values on the Hyper-V nodes to 1 accordingly. In contrast to the commandlet documentation, the value is not 2, which would make more sense.

Quite unknown, as not documented in the LCU KB5017381 itself, but only referenced in the documentation for the PowerShell commandlet Get-Cluster.
Frankly, none of the aren't areas customers nor partners would check quite regularly to spot any of such relevant feature improvements or changes.

"Beginning with the 2022-09 Cumulative Update, you can now configure the number of parallel live migrations within a cluster. For more information, see KB5017381 for Windows Server 2022 and  KB5017382 for Azure Stack HCI (Azure Local), version 21H2.

(Get-Cluster).MaximumParallelMigrations = 2

 

The example above sets the cluster property MaximumParallelMigrations to a value of 2, limiting the number of live migrations that a cluster node can participate in. Both existing and new cluster nodes inherit this value of 2 because it's a cluster property. Setting the cluster property overrides any values configured using the Set-VMHost command." 

Network ATC in Azure Local 22H2+ and Windows Server 2025+:
When using Network ATC in Windows Server 2025 and Azure Local, it will set the live migration to 1 per default and enforce this across all cluster nodes. Disregarding the Cluster Settings above or Local Hyper-V Settings. To change the number of live migration you can specify a cluster-wide override  in Network ATC.

Conclusion:
The default values for live migration have been changes. The global cluster setting or Network ATC forcing these down to the Hyper-V hosts based on Windows Server 2022+/ Azure Local nodes and ensure consistency.

Previously we thought this would happen after using Windows Admin Center (WAC) when opening the WAC cluster settings, but this was not the initial cause.

Finding references:

Later the day, as my interest grew about this change I found an official announcement.

In agreement to another article, on optimizing live migrations, the default value should be 2, but for some reason at most customers, even on fresh installations and clusters, it is set to 1.


TLDR:
1. Stop bothering on changing the Livemigration setting manually or PowerShell or DSC / Policy.

2. Today and in future train your muscle memory to change live migration at cluster level with Get-Cluster, or via Network ATC overrides. These will be forced down quite immediately to all nodes and will be automatically corrected if there is any configuration drift on a node.

3. Check and set the live migration value to 2 as per default and follow these recommendations:

Optimizing Hyper-V Live Migrations on an Hyperconverged Infrastructure | Microsoft Community Hub
Optimizing your Hyper-V hosts | Microsoft Community Hub

4. You can stop blaming WAC or overeager colleagues for changing the LM settings to undesirable values over and over. Starting with Windows Admin Center (WAC) 2306, you can set the Live Migration Settings at cluster level in Cluster > Settings.


Happy Clustering! 😀