VMware vMotion is the core live migration capability used to move running workloads with minimal disruption. If it is not planned correctly, routine maintenance windows can quickly turn into avoidable production incidents.
Short answer: vMotion transfers a VM runtime state (memory, registers, network identity) to a compatible target host so services can continue with minimal interruption.
Quick Summary
- Broadcom TechDocs states that with vMotion, VM processes continue running during migration.
- Main migration types are Cold Migration, Hot Migration (vMotion), and Storage vMotion.
- The migration wizard runs compatibility checks against destination host/cluster criteria before execution.
- CPU compatibility baseline: source and destination CPUs must be in the same vendor class (AMD or Intel).
- EVC improves interoperability by masking CPU features to a shared baseline mode.
- Encrypted vMotion secures confidentiality, integrity, and authenticity of migration traffic; for unencrypted VMs,
Opportunisticis default andRequiredenforces encryption. - In the vCenter simultaneous migration table (vSphere 6.0-8.0 row), derived host limits are vMotion: 8, Storage vMotion: 2, vMotion Without Shared Storage: 2.
Table of Contents
- What Is VMware vMotion
- How vMotion Works
- Migration Types and Correct Usage
- vMotion Prerequisites
- Traffic Isolation with vMotion TCP/IP Stack
- When to Use Encrypted vMotion
- Simultaneous Migration Limits
- Frequently Asked Questions
Image: Wikimedia Commons - Photo of New Orleans Data Center.
What Is VMware vMotion
vMotion is a live migration feature that moves a powered-on VM between ESXi hosts. The goal is not only relocation, but continuity.
Typical use cases:
- Draining hosts before planned maintenance
- Rebalancing cluster capacity
- Moving workloads away from degraded hosts
How vMotion Works
At a high level:
- Compatibility validation: destination host/cluster checks are executed by the migration wizard.
- State transfer: VM runtime data is copied to the target.
- Cutover: execution continues on the destination host with a short transition window.
This approach makes maintenance windows safer in production environments.
Migration Types and Correct Usage
Cold Migration
Moves powered-off or suspended VMs across hosts/datastores.
Hot Migration (vMotion)
Moves powered-on VMs across compute resources with minimal disruption.
Storage vMotion
Moves VM disks to another datastore while the VM keeps running.
vMotion Prerequisites
Most migration failures come from missing prerequisites:
- CPU compatibility: source and destination hosts must be in the same vendor class.
- EVC baseline: required for many heterogeneous clusters.
- vMotion network readiness: source/target hosts must be configured correctly.
- Wizard compatibility results: warnings and errors must be interpreted correctly before execution.
Traffic Isolation with vMotion TCP/IP Stack
TechDocs explicitly separates migration traffic models:
- vMotion TCP/IP stack: isolates live migration traffic.
- Provisioning TCP/IP stack: isolates cold migration, clone, and snapshot traffic.
This improves operational control over routing, gateway, and DNS behavior for migration paths.
When to Use Encrypted vMotion
Encrypted vMotion protects migration traffic confidentiality, integrity, and authenticity.
For unencrypted VMs:
- Opportunistic (default): encrypt if both hosts support encrypted vMotion.
- Required: allow only encrypted migration; fail if unsupported.
Required is generally safer in regulated or multi-tenant environments.
Simultaneous Migration Limits
Use vCenter limits directly for planning migration windows.
Example (vSphere 6.0-8.0 row):
| Operation | Derived Limit Per Host | Host Resource Cost |
|---|---|---|
| vMotion | 8 | 1 |
| Storage vMotion | 2 | 4 |
| vMotion Without Shared Storage | 2 | 4 |
These values are important when scheduling parallel maintenance operations.
Practical Operations Note
In multi-site environments, including enterprise teams around Ankara, vMotion should be treated as a repeatable operating standard rather than a one-off action.
Recommended baseline runbook:
- Daily: host health and alarm review
- Weekly: EVC and compatibility risk sweep
- Monthly: migration capacity drill for maintenance scenarios
Frequently Asked Questions
What is the difference between vMotion and Storage vMotion?
vMotion moves compute runtime; Storage vMotion moves disk location while running. They can be combined when needed.
Is shared storage always required?
Traditional patterns rely on it, but TechDocs also covers supported scenarios without shared storage.
Can I vMotion from Intel to AMD hosts?
Not in standard compatibility flow. The official guidance requires same vendor class.
What is the most critical pre-check?
Migration wizard compatibility output. Ignoring blocking errors introduces avoidable production risk.
Conclusion
When designed correctly, vMotion turns maintenance from outage-focused work into continuity-focused operations. Compatibility checks, EVC strategy, traffic isolation, and migration concurrency limits should be handled as one operating model.
For environment-specific vMotion planning, you can contact our team.
Sources
- Broadcom TechDocs - vSphere Virtual Machines Migration
- Broadcom TechDocs - Migrating Virtual Machines with vSphere vMotion
- Broadcom TechDocs - vMotion Migration Compatibility Checks
- Broadcom TechDocs - CPU Compatibility and vSphere Enhanced vMotion Compatibility
- Broadcom TechDocs - How to Isolate Traffic for Migrating Your Virtual Machines
- Broadcom TechDocs - What Is Encrypted vSphere vMotion
- Broadcom TechDocs - vCenter Server Limits on Simultaneous Migrations
- Broadcom TechDocs - Migrating Virtual Machines Between vCenter Server Systems
- Wikimedia Commons - NOIRLab HQ Server Racks (6V6A0404-CC)
