What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
Affinity rules keep selected virtual machines together; anti-affinity rules keep them apart. The placement scope matters: a rule can target the same or different node, or the same or different fault domain. Microsoft’s current documentation calls the platform Azure Local and applies its guidance to Azure Local 2311.2 and later, so older Azure Stack HCI releases may differ. Microsoft Learn: VM affinity rules
Choose the placement scope that matches the requirement
“Together” and “apart” describe the direction of a rule, but not how broadly it applies. In PowerShell, the four rule types distinguish node placement from fault-domain placement:
| # | Preview | Product | Price | |
|---|---|---|---|---|
| 1 |
|
The Definitive Guide to Building S2D Clusters RealWorld Insights on Design and Operations to Avoid... | $6.31 | Buy on Amazon |
| Rule type | Placement effect | Use it when |
|---|---|---|
SameNode |
Keep the selected groups on the same machine. | Workloads or a VM and its storage need node-level co-location. |
DifferentNode |
Keep the selected groups on different machines. | You need workload separation between nodes. |
SameFaultDomain |
Keep the selected groups in the same fault domain or site. | Workloads should share a site but do not necessarily need the same node. |
DifferentFaultDomain |
Keep the selected groups in different fault domains or sites. | You need separation across a fault boundary. |
For example, a SQL VM and a web VM might need to remain in the same site while running on separate machines. That calls for a fault-domain scope and a node-level separation requirement—not simply a generic “apart” rule. Microsoft’s documentation also demonstrates using a same-node rule when workloads must run together. Avoid treating site-level placement as interchangeable with Azure Availability Zones; the cited guidance does not establish that equivalence.
When to use affinity and anti-affinity
Use anti-affinity to reduce shared-node contention or failure exposure
Anti-affinity can separate resource-intensive VMs so they do not compete for CPU, memory, or storage on one machine. It can also help distribute domain controllers across machines or sites, reducing the chance that a single node or site failure affects every instance. Microsoft’s Azure Local Well-Architected guidance recommends at least two instances of each critical workload tier and says, “On standard clusters, use VM anti-affinity rules where supported.” Microsoft Azure Well-Architected: Azure Local
The Tool Desk
Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →A placement rule is only one part of resilience: it does not create extra workload instances or replace a design for recovery across the relevant failure boundary. Choose node separation when a machine-level failure or contention is the concern; choose fault-domain separation when the design must withstand a site or other fault-domain failure.
Use affinity when co-location is intentional
Affinity is useful when two resources need to run together, or when a workload should remain within a particular fault domain. One documented storage pattern associates a VM with its VHDX on a Cluster Shared Volume (CSV) using a SameNode rule. Microsoft says this can avoid CSV redirection, which may slow VM start or stop. This is a configuration option, not a universal performance recommendation or a guarantee that every cluster topology benefits.
Create a basic rule in Windows Admin Center
Windows Admin Center provides the basic choices “Together (same machine)” and “Apart (different machines).” Microsoft documents this flow:
- Select the machine or system in Windows Admin Center.
- Open Settings > Affinity rules.
- Create a named rule and select Together or Apart.
- Choose the VMs to include and create the rule.
These basic choices address machine-level placement. If you need to express same-site or different-site placement, or configure more complex relationships, use PowerShell’s more specific rule types and configuration options. See Microsoft’s affinity-rule procedure for the current documented workflow.
Configure rules with PowerShell
PowerShell offers more control than the basic Windows Admin Center choices. Microsoft’s documented cmdlets include New-ClusterAffinityRule to create a rule, Add-ClusterGroupToAffinityRule to add groups, Set-ClusterAffinityRule to configure it, and Get-ClusterAffinityRule to inspect rules. Use the official procedure for the command syntax, required parameters, and cluster or management-computer context; the cmdlet names alone are not a complete, copy-ready command sequence. Microsoft Learn: PowerShell steps and examples
VM-to-CSV storage affinity
Microsoft’s example creates a SameNode rule, adds the VM group and CSV to that rule, and enables it. Follow the documented example for exact commands and parameters rather than assuming a generic sequence will fit every cluster. Whether this arrangement is appropriate depends on the storage and cluster design; the example does not establish a measured performance gain.
Understand the Azure Arc management boundary
Microsoft says, “The recommended way to create and manage VMs on Azure Local is using the Azure Arc control plane.” Its VM-affinity documentation immediately qualifies that guidance: the affinity functionality described there is not yet provided by Azure Arc. For these rule operations, use Windows Admin Center or PowerShell. Microsoft’s supported-operations list also identifies affinity and anti-affinity as operations supported only through local tools. Microsoft Learn: supported Azure Arc VM operations
VMs created through this local-tool workflow have limited manageability through the Arc control plane and fewer Azure Hybrid Benefits, as Microsoft explains in its affinity documentation. Account for that management trade-off before choosing the workflow.
Rack-aware clusters require a separate check
Do not assume the standard-cluster procedures above are validated for rack-aware deployments. Microsoft warns that applying VM affinity rules through Windows Admin Center or PowerShell on rack-aware clusters can result in unknown behavior. Its rack-aware guidance discusses separate availability-zone placement and cautions against affinity rules in that context. Check the applicable rack-aware design guidance before configuring placement; Microsoft’s rack-aware cluster requirements describes the relevant support constraints.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
