How to Configure EVC Mode in vSphere: Complete Setup Guide for Enhanced vMotion Compatibility

As virtualization environments grow and evolve, IT administrators face a common challenge: maintaining workload mobility across ESXi hosts with different CPU generations. This is where Enhanced vMotion Compatibility (EVC) becomes essential. In this comprehensive guide, I’ll walk you through everything you need to know about configuring EVC mode in VMware vSphere, based on real-world experience and best practices.

What is EVC Mode in vSphere?

Enhanced vMotion Compatibility (EVC) is a vSphere cluster feature that ensures virtual machines can seamlessly migrate between ESXi hosts running different CPU generations from the same vendor. Think of it as a CPU instruction set equalizer that creates a uniform computing baseline across your cluster.

When you enable EVC, vSphere masks certain CPU features on newer processors to match the capabilities of older ones in the cluster. This creates a consistent CPU instruction set (CPUID baseline) that all VMs see, regardless of which physical host they’re running on.

Why EVC Mode Matters

In today’s dynamic data centers, you’ll likely encounter this scenario: your three-year-old servers need expansion, but those original processors are no longer available. Without EVC, adding new hosts with modern CPUs would prevent live migrations between old and new hardware. EVC solves this challenge elegantly.

The feature has zero performance overhead on your infrastructure. While newer CPU instructions may be masked, your existing workloads continue performing as before, and you gain the critical ability to scale your cluster without downtime.

EVC Mode Requirements and Prerequisites

Before diving into configuration, ensure your environment meets these essential requirements:

Hardware Requirements

• CPU Vendor Consistency: All ESXi hosts must use processors from the same vendor—either all Intel or all AMD
• Virtualization Extensions: Intel VT-x or AMD-V must be enabled in the UEFI/BIOS of all ESXi hosts
• Compatible CPU Generations: Processors should support a common EVC baseline

Software Requirements

• vCenter Server: All hosts must be managed by the same vCenter Server instance
• vMotion Configuration: vMotion must be properly configured and functional
• VM Hardware Version: For per-VM EVC, virtual machines require hardware version 14 or higher (introduced in vSphere 6.7)

Important Considerations

The EVC baseline you can select is determined by the oldest processor in your cluster. While you can technically choose an even older baseline, there’s rarely a practical reason to do so. The VMware Compatibility Guide is your best resource for identifying which EVC modes work with your specific processors.

Understanding EVC Baselines

EVC baselines correspond closely to specific processor generations and their feature sets. For example:

Intel Baselines

• Intel Penryn Generation
• Intel Nehalem Generation
• Intel Westmere Generation
• Intel Sandy Bridge Generation
• Intel Ivy Bridge Generation
• Intel Haswell Generation
• Intel Broadwell Generation
• Intel Skylake Generation
• Intel Cascade Lake Generation

AMD Baselines

• AMD Opteron Generation 3
• AMD Opteron Generation 4
• AMD Bulldozer Generation
• AMD Piledriver Generation
• AMD EPYC Generation 1
• AMD EPYC Generation 2

Each successive generation includes additional CPU instructions. When you select a baseline, VMs can only access instructions available in that generation, even if the physical processor supports more advanced features.

How to Enable EVC Mode on a New vSphere Cluster

Enabling EVC when creating a new cluster is the ideal approach—it prevents complications later. Here’s the step-by-step process:

Step 1: Verify CPU Configuration

1. Open VMware vSphere Client and log in to your vCenter Server
2. Navigate to Hosts and Clusters
3. Select each ESXi host individually
4. Review the CPU information in the Summary tab
5. Note the processor models and generations

Step 2: Check VMware Compatibility Guide

1. Open the VMware Compatibility Guide in a separate browser tab
2. Select your CPU series and ESXi version
3. Click CPU / EVC Matrix
4. Identify the appropriate EVC baseline for your oldest processor

Step 3: Create Cluster with EVC Enabled

1. Right-click your datacenter and select New Cluster
2. Name your cluster
3. In the cluster creation wizard, check Enable EVC
4. Select your CPU vendor (Intel or AMD)
5. Choose the appropriate EVC mode baseline from the dropdown menu
6. Review the validation message at the bottom—it should show “Validation succeeded”
7. Complete the cluster creation

Step 4: Add Hosts to the Cluster

1. Drag and drop ESXi hosts into your new EVC-enabled cluster, or
2. Right-click hosts and select Move To → Select your cluster
3. Hosts are automatically configured with the cluster’s EVC settings

Enabling EVC Mode on an Existing Cluster

Enabling EVC on a cluster with running workloads requires more careful planning. Here’s the process:

For Clusters with Powered-Off VMs

1. Navigate to your cluster in vSphere Client
2. Click the Configure tab
3. Select VMware EVC under Configuration
4. Click Edit
5. Select Enable EVC for [Intel/AMD] Hosts
6. Choose your EVC mode baseline
7. Review compatibility validation
8. Click OK to apply

For Clusters with Running VMs

This scenario is more complex. You have several options:

Option 1: Selective Shutdown (Recommended)

• If VMs are running on the ESXi host with the oldest processor
• AND the EVC baseline matches that processor’s generation
• AND you’re using standard vSwitches (not distributed vSwitches)
• You may be able to enable EVC without shutting down those VMs
• All other VMs must be powered off first

Option 2: Complete Shutdown

1. Migrate or shut down all virtual machines
2. Temporarily remove hosts from the cluster if necessary
3. Enable EVC on the empty cluster
4. Add hosts back to the cluster
5. Power on virtual machines

Option 3: Create Temporary Cluster (For vCenter Server as VM) This is necessary when vCenter itself runs as a VM in the cluster you want to enable EVC on:

1. Create a new temporary cluster
2. Enable EVC immediately on the empty cluster
3. Move one ESXi host to the temporary cluster
4. Use Storage vMotion to move the vCenter VM to shared storage accessible from both clusters
5. Register the vCenter VM on the host in the EVC-enabled cluster
6. Continue enabling EVC on the original cluster
7. Migrate VMs back once complete

Critical Note About VM Power Cycles

After enabling or changing EVC mode, you must power off and power on affected VMs (not just reboot). A simple reboot doesn’t apply the new CPUID settings. The VMs need a full power cycle to pick up the configured EVC baseline.

Configuring Per-VM EVC Mode

Since vSphere 6.7, you can set EVC mode at the individual VM level, providing greater flexibility for hybrid cloud and cross-cluster migrations.

When to Use Per-VM EVC

• Migrating VMs between different clusters with varying EVC settings
• Moving workloads across vCenter Server instances
• Preparing VMs for cloud migration (AWS, Azure, VMware Cloud)
• Granular control over CPU feature sets for specific applications

How to Configure Per-VM EVC

1. Ensure the VM has hardware version 14 or higher
2. Power off the virtual machine
3. In vSphere Client, select the VM
4. Click the Configure tab
5. Select VMware EVC under VM Hardware
6. Click Edit
7. Select Activate EVC
8. Choose a CPU mode baseline from the dropdown
9. Verify the baseline doesn’t exceed the cluster’s EVC mode (if applicable)
10. Click OK
11. Power on the VM

The per-VM EVC configuration is stored in the VM’s .vmx file and travels with the VM during migrations. You’ll see entries like:

featMask.vm.cpuid.Intel = "Val:1"
featMask.vm.cpuid.FAMILY = "Val:6"
featMask.vm.cpuid.MODEL = "Val:0x4f"

Important: If a VM’s per-VM EVC baseline exceeds what the ESXi hosts support, the VM will fail to power on.

Changing EVC Mode on an Existing Cluster

Sometimes you need to adjust your cluster’s EVC baseline—perhaps after retiring older hosts or adding newer hardware.

Raising the EVC Baseline

You can increase the EVC mode when all hosts in the cluster support the higher baseline:

1. Navigate to cluster → Configure → VMware EVC
2. Click Edit
3. Select a higher EVC mode from the dropdown
4. Review validation results
5. Click OK
6. Power off and power on VMs to apply the new baseline

Lowering the EVC Baseline

Reducing the EVC baseline is more restrictive:

1. Power off ALL virtual machines in the cluster
2. Navigate to cluster → Configure → VMware EVC
3. Click Edit
4. Select a lower EVC mode
5. Click OK
6. Power on VMs

Verifying EVC Configuration

After configuring EVC, verify everything is working correctly:

Check Cluster EVC Status

1. Select your cluster
2. Click Configure tab
3. Select VMware EVC
4. Verify EVC mode is shown as enabled with correct baseline
5. Review Current CPUID Details for mask values

Test vMotion Between Hosts

1. Select a powered-on VM
2. Right-click and choose Migrate
3. Select Change compute resource only
4. Choose a different host in the cluster
5. Complete the migration
6. Verify the VM operates normally

Use PowerCLI for Bulk Verification

powershell

Get-Cluster | Select Name, EVCMode
Get-VM | Select Name, @{N="VM Hardware Version";E={$_.Version}}, @{N="Per-VM EVC";E={$_.ExtensionData.Runtime.MinRequiredEVCModeKey}}

Common EVC Configuration Issues and Solutions

Issue 1: “Host cannot be admitted to cluster”

Cause: The host’s CPU doesn’t support the cluster’s EVC baseline, or features are hidden by the EVC mode.

Solution:

• Verify CPU compatibility in VMware Compatibility Guide
• Check BIOS/UEFI settings for disabled CPU features
• Consider lowering the cluster EVC baseline if appropriate

Issue 2: “Cannot enable EVC with running VMs”

Cause: VMs are using CPU features that would be masked by the EVC mode.

Solution:

• Power off affected VMs
• Enable EVC
• Power on VMs to apply new CPUID baseline

Issue 3: vCenter VM prevents EVC enablement

Cause: The vCenter Server VM itself needs to be powered off, but it’s required to enable EVC.

Solution: Use the temporary cluster method described earlier.

Issue 4: Per-VM EVC prevents VM from powering on

Cause: The VM’s EVC baseline exceeds what cluster hosts support.

Solution:

• Power off the VM
• Lower the per-VM EVC baseline
• Ensure it doesn’t exceed cluster EVC mode
• Power on the VM

Issue 5: TSX instructions causing compatibility issues

Cause: Intel’s Transactional Synchronization Extensions may be disabled via microcode on Haswell processors.

Solution: If TSX is disabled, select the Ivy Bridge EVC baseline instead of Haswell.

Best Practices for EVC Configuration

Based on practical experience managing EVC across numerous environments, here are proven best practices:

1. Enable EVC from Day One

The easiest time to enable EVC is when creating a new cluster. Even if you have uniform hardware today, enabling EVC costs nothing and provides future flexibility.

2. Select the Appropriate Baseline

Choose the EVC baseline that matches your oldest processor. Don’t select an older baseline than necessary—it unnecessarily limits available CPU features.

3. Document Your EVC Strategy

Maintain clear documentation including:

• Current EVC baseline and rationale
• Processor models in each cluster
• Future hardware refresh plans
• Any per-VM EVC configurations

4. Plan Hardware Refresh with EVC in Mind

When planning hardware purchases, consider:

• How the new processors will affect your EVC baseline
• Whether you can raise the EVC mode after old hardware is retired
• Compatibility between processor generations

5. Use Per-VM EVC for Hybrid Cloud

If you’re planning cloud migrations or multi-cluster workloads, implement per-VM EVC to maintain flexibility.

6. Monitor Performance After Changes

While EVC has no inherent performance penalty, monitor applications after:

• Enabling EVC
• Changing EVC baselines
• Migrating VMs between different EVC environments

7. Test Before Production

In lab or staging environments:

• Test EVC enablement procedures
• Verify application compatibility
• Practice VM migrations between different EVC modes

8. Stay Current with vCenter Server

Newer vCenter versions support the latest CPU generations and EVC baselines. Keeping vCenter updated ensures you can leverage modern hardware.

9. Regular Compatibility Reviews

Periodically review:

• VMware Compatibility Guide for new EVC modes
• Hardware in your clusters
• Whether EVC baselines can be raised

10. Understand the Limitations

Remember that EVC:

• Only works within the same CPU vendor (Intel or AMD)
• Masks features but doesn’t emulate missing ones
• Requires proper planning in existing environments
• Doesn’t affect storage vMotion operations

EVC Mode and vSphere Features

Understanding how EVC interacts with other vSphere features helps you design robust solutions:

vSphere HA (High Availability)

EVC doesn’t impact HA functionality. When HA restarts a VM on a different host, the VM is power-cycled, automatically picking up the correct CPUID from the new host.

vSphere DRS (Distributed Resource Scheduler)

DRS works seamlessly with EVC. The uniform CPU baseline ensures DRS can balance workloads across all cluster hosts without compatibility concerns.

vSphere vMotion

This is EVC’s primary purpose—enabling live migration between hosts with different CPU generations. With EVC enabled, vMotion operates normally across dissimilar hardware.

Storage vMotion

Storage vMotion is unaffected by EVC settings. You can migrate VM storage regardless of EVC configuration.

Fault Tolerance (FT)

Fault Tolerance requires even stricter CPU compatibility than standard vMotion. Ensure your EVC baseline supports FT requirements for critical VMs.

Performance Considerations

A common concern is whether EVC impacts VM performance. Here’s what you need to know:

The Reality of EVC Performance

• EVC itself has zero overhead
• Masking CPU features doesn’t slow down existing instructions
• VMs only “lose” access to instructions that weren’t available on older processors anyway
• If all your hosts have identical processors, there’s no practical performance difference with EVC enabled

When Performance Might Be Affected

Performance considerations arise when:

• Adding much older hosts to a cluster with newer processors
• The EVC baseline is significantly older than your newest hardware
• Applications specifically require instruction sets that get masked

Measuring Impact

VMware’s own testing shows minimal performance differences across most workloads. For latency-sensitive or compute-intensive applications, consider:

• Testing applications with and without EVC
• Using per-VM EVC to give critical VMs higher baselines
• Maintaining separate clusters for extreme performance requirements

Future-Proofing Your EVC Strategy

As virtualization continues evolving, keep these trends in mind:

Custom EVC (vSphere 9.0+)

VMware introduced Custom EVC, allowing you to define baselines based on the common features of specific hosts, rather than predetermined generations. This provides more flexibility than traditional EVC baselines.

GPU EVC

For workloads using graphics processors, vSphere 7 Update 1 introduced EVC for GPU, enabling vMotion between hosts with different GPU models while maintaining graphics compatibility.

Cloud Integration

With increasing hybrid and multi-cloud adoption, per-VM EVC becomes critical for workload portability between on-premises and cloud environments.

Conclusion

Enhanced vMotion Compatibility is one of those vSphere features that seems complex initially but becomes indispensable once you understand it. By creating a uniform CPU instruction baseline across your cluster, EVC ensures your virtualization environment remains flexible and scalable as hardware evolves.

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