VMware ESXi and vSphere Cluster Management
Enhanced vMotion Compatibility (EVC) Cluster Requirements
Learn the CPU, firmware, networking, vCenter Server, and ESX/ESXi version requirements for configuring an EVC-enabled cluster.
Enhanced vMotion Compatibility (EVC) is a vSphere cluster feature that establishes a common CPU instruction-set baseline for virtual machines. The baseline allows a running virtual machine to move with vMotion, which is the live migration of a running virtual machine, between compatible hosts that use different processor models.
EVC is a planning tool as much as a configuration feature. Before adding hosts and migration-dependent workloads to a cluster, verify that the hosts use the same CPU vendor, meet the required processor generations, expose the required firmware features, run a supported ESX/ESXi version, and have usable vMotion networking.
What EVC Provides
An EVC baseline, also called an EVC mode, is the CPU feature level selected for a cluster. EVC presents that common level to virtual machines so a VM does not depend on processor instructions available only on a newer host.
The central scenario is a same-vendor, different-generation cluster. For example, several Intel hosts may use different Intel CPU models. If all hosts can support one common EVC baseline, vMotion can use that baseline when moving workloads between them.
EVC is intended for processors from the same vendor family and a compatible generation range. It is not a method for combining Intel and AMD hosts into one EVC cluster.
CPU Vendor and Family Compatibility
Same manufacturer is required
Every host in an EVC cluster must use CPUs from the same manufacturer. Intel and AMD processors cannot be mixed in the same EVC cluster.
- Permitted scenario: different Intel CPU models that share a supported EVC baseline.
- Permitted scenario: different AMD Opteron generations that share a supported EVC baseline.
- Not permitted: a cluster containing both Intel-based and AMD-based hosts.
A CPU family is a related processor lineage from one vendor. Different models may be usable together when they belong to a supported family range and the oldest or least capable host supports the selected baseline.
Minimum processor generations
For the requirement described here, Intel processors must be based on the Core 2 microarchitecture or later. AMD hosts must use first-generation AMD Opteron processors or later.
These generation requirements are only a starting point. The selected EVC mode must be supported by every host. In practice, evaluate the oldest or least capable processor first, because it commonly determines the highest baseline the entire cluster can use.
Required Host Hardware Features
Hardware-assisted virtualization
Hardware virtualization means the processor virtualization extensions used by the hypervisor, such as Intel virtualization support or AMD virtualization support. Hardware-assisted virtualization must be enabled on every ESX/ESXi host in the cluster.
Enable this setting in each server's BIOS or firmware. The setting name varies by server and processor generation, so consult the server firmware interface for the vendor-specific label. A host with the feature disabled is not consistently eligible for the cluster.
NX or XD protection
Each host must also expose its processor execution-disable feature:
- AMD hosts require AMD No eXecute (NX).
- Intel hosts require Intel eXecute Disable (XD).
NX and XD are processor protection features. Enable the appropriate feature on every host in system BIOS or firmware before enabling EVC. A supported CPU does not satisfy this requirement if the feature is disabled or unavailable to ESX/ESXi.
Software and Management Requirements
vCenter Server management
EVC requires a cluster managed by vCenter Server, the centralized management platform for vSphere. EVC is a cluster-level capability, so it is not available when hosts are administered only as independent, standalone hosts.
Place all participating hosts under the same vCenter Server management structure and configure them as members of the intended cluster. For related host inventory tasks, see Add ESXi Host to vCenter Server Inventory.
ESX/ESXi version
Every participating host must run ESX/ESXi 3.5 Update 2 or later. Do not attempt to enable EVC while any host is below this minimum. Version consistency and upgrade planning should be checked before host admission.
vMotion Network Readiness
vMotion networking must be configured for every host in the cluster. Each host needs a usable vMotion-enabled network path with connectivity to the other hosts that may receive migrated virtual machines.
EVC handles CPU feature compatibility; it does not configure the network, provide reachability, or replace other vMotion requirements. Validate the vMotion network independently of the CPU checks.
- Confirm that each host has a vMotion-enabled network configuration.
- Confirm that the vMotion path is usable between relevant hosts.
- Check the configuration again after adding or replacing a host.
For broader migration planning, review VMware ESXi Online Course and the vCenter-to-host communication concepts in Communication Between vCenter Server and ESXi.
EVC Prerequisite Checklist
| Requirement | Applies to | Expected condition | How to validate | Effect if unmet |
|---|---|---|---|---|
| CPU vendor consistency | All hosts | Every host uses the same CPU manufacturer. | Inventory the processor vendor on each host. | Intel and AMD hosts cannot share an EVC cluster. |
| Common CPU family or baseline | All hosts | All processors can support one common EVC baseline. | Compare the selected baseline with the oldest or least capable host. | EVC cannot be enabled at that baseline. |
| Intel minimum generation | Intel hosts | Core 2 microarchitecture or later. | Identify each processor model and generation. | An older host does not meet the stated requirement. |
| AMD minimum generation | AMD hosts | First-generation AMD Opteron or later. | Identify each processor model and generation. | An older host does not meet the stated requirement. |
| Hardware virtualization | Every host | CPU virtualization extensions are enabled. | Inspect BIOS or firmware and confirm the host exposes the feature. | The host fails the hardware prerequisite. |
| AMD NX or Intel XD | Every host | NX is enabled on AMD or XD is enabled on Intel. | Inspect the corresponding BIOS or firmware setting. | The host must be corrected before EVC is enabled. |
| vMotion networking | Every host | A configured, reachable vMotion-enabled network path exists. | Review host networking and validate connectivity. | EVC may be configured, but live migration cannot use that host. |
| vCenter Server management | Cluster | The cluster and all hosts are managed by vCenter Server. | Verify host inventory and cluster membership in vCenter Server. | Standalone host administration does not provide EVC. |
| Minimum ESX/ESXi version | Every host | ESX/ESXi 3.5 Update 2 or later. | Check the installed host version. | The host cannot participate until upgraded or removed. |
Pre-Enable Validation Workflow
- Inventory CPUs: record the vendor, model, family, and generation for every proposed host.
- Separate vendors: remove or place elsewhere any host that uses a different CPU manufacturer. Do not mix Intel and AMD in one EVC cluster.
- Find the limiting host: identify the oldest or least capable processor and select only a baseline that every host supports.
- Check firmware: enable hardware-assisted virtualization on every host.
- Check NX or XD: enable AMD NX or Intel XD on every host, as appropriate.
- Check software: verify that every host runs ESX/ESXi 3.5 Update 2 or later.
- Check management: confirm that vCenter Server manages the hosts and that they belong to the intended cluster.
- Check migration networking: verify a usable vMotion-enabled network path on every host.
- Resolve exceptions: correct, upgrade, replace, or separate every noncompliant host before attempting to enable EVC.
- Select the baseline: configure an EVC mode supported by all remaining hosts, then recheck the cluster.
Supported and Unsupported Cluster Compositions
| Host CPU makeup | EVC eligibility outcome | Reason |
|---|---|---|
| Different Intel models with a shared baseline | Potentially eligible | All hosts use one vendor and can expose the same selected CPU feature level. |
| Different AMD Opteron models with a shared baseline | Potentially eligible | All hosts use AMD Opteron processors and the baseline is supported by every host. |
| Mixed Intel and AMD hosts | Unsupported | EVC does not permit mixing CPU vendors in one cluster. |
| A host below the required generation | Unsupported as proposed | The host fails the stated minimum generation or may prevent a common baseline. |
| A host missing required firmware features | Not ready | Hardware virtualization or NX/XD must be enabled before the host can satisfy the prerequisites. |
Practical Examples
Compatible Intel cluster
A cluster contains different Intel CPU models, all based on Core 2 or later. Every host supports the selected EVC baseline, has hardware virtualization and XD enabled, runs ESX/ESXi 3.5 Update 2 or later, is managed by vCenter Server, and has vMotion networking. This cluster meets the stated requirements.
Compatible AMD cluster
A cluster contains AMD Opteron hosts from different generations. Start with the oldest host when choosing the baseline, then confirm that every host supports it and that NX is enabled throughout the cluster.
Mixed-vendor cluster
A cluster contains both Intel-based and AMD-based hosts. It cannot use EVC. Separate the hosts into compatible clusters or redesign the placement so each EVC cluster contains one CPU vendor.
Firmware configuration blocker
A host has an otherwise supported processor, but hardware virtualization or NX/XD is disabled in BIOS or firmware. Enable the missing feature, allow the host to boot with the new setting, and repeat the eligibility checks.
Migration network blocker
All processors support the selected baseline, but one host has no usable vMotion network. EVC does not solve this problem. Configure and validate vMotion networking on that host before relying on migration.
Troubleshooting EVC Prerequisite Failures
EVC reports incompatible processors
Likely causes include a mixed Intel and AMD cluster, a host that cannot support the selected baseline, or a processor older than the stated minimum generation. Use one CPU vendor, choose a baseline supported by every host, and remove, replace, upgrade, or separate incompatible hosts.
A supported CPU still fails the checks
Check BIOS or firmware. Hardware virtualization may be disabled, or NX on AMD and XD on Intel may not be enabled. Correct the setting on the affected host and run the checks again.
EVC is configured but vMotion fails for one host
Inspect that host's vMotion-enabled network and its connectivity to the other hosts. EVC provides a CPU compatibility baseline but does not create the network path required for live migration.
A host cannot join the EVC cluster
Confirm that vCenter Server manages the host and that the host runs ESX/ESXi 3.5 Update 2 or later. Add it to vCenter Server inventory or upgrade it as needed, then validate CPU and firmware requirements again.
Exam-Relevant Notes
- EVC establishes a common CPU instruction-set baseline for vMotion compatibility.
- All hosts in one EVC cluster must use the same CPU manufacturer; Intel and AMD cannot be mixed.
- The described minimum generations are Intel Core 2 microarchitecture or later and first-generation AMD Opteron or later.
- Hardware-assisted virtualization and the relevant NX or XD feature must be enabled on every host in BIOS or firmware.
- Every host needs vMotion networking, and EVC does not replace that requirement.
- EVC requires a vCenter Server-managed cluster and ESX/ESXi 3.5 Update 2 or later on all participating hosts.
- The selected EVC baseline must be supported by the oldest or least capable host as well as every other host.