Hot vs Cold Migration in VMware: Differences, Requirements, Steps, and When to Use Each

Hot migration in VMware means moving a powered-on VM with minimal disruption (typically via vMotion), while cold migration means moving it powered off (planned downtime). In practice, your choice depends on downtime tolerance, host CPU/EVC compatibility, storage needs (Storage vMotion), and network readiness. In this guide, we’ll walk through a clear comparison table, a simple decision flow, prerequisites, step-by-step execution, validation, and troubleshooting so you can migrate confidently and avoid the common pitfalls. Read on and we’ll make the decision and the execution feel straightforward.

Quick answer: what’s the difference between hot and cold migration?

Hot migration (commonly referring to vMotion) moves a VM while it stays powered on, so the application remains available with minimal disruption. VMware describes vMotion as the mechanism for migrating powered-on VMs, while cold migration applies to powered-off or suspended VMs.

Cold migration moves the VM when it’s powered off (or suspended), which means downtime is expected, but it’s also the practical option when live migration isn’t possible due to CPU mismatch, network constraints, or planned maintenance windows.

Storage vMotion is a close cousin: it moves the VM’s disk files from one datastore to another while the VM is running, typically used for storage maintenance, rebalancing, or datastore consolidation.

Don’t confuse these: the VMware migration taxonomy

A lot of confusion comes from using “hot/cold migration” as a catch-all. Here’s the clean taxonomy:

• Compute vMotion (hot): VM stays powered on and changes host (compute resource)
• Storage vMotion (hot): VM stays powered on and changes datastore (storage location)
• Combined compute + storage migration (hot): VM stays powered on and changes both host and datastore (where supported)
• Cold migration: VM is powered off or suspended during the move

One more nuance you’ll see in real environments: “cold data” moved during a hot migration. Even when a VM stays online, certain file copy operations (snapshots, configuration elements, or storage-related transfers) may not behave the way people expect, so it helps to understand which network and pathway the platform uses.

One-screen comparison: hot vs cold vs Storage vMotion

If you only remember one thing: hot migration protects availability; cold migration protects compatibility.

Decision flowchart: which migration should you use?

Use this as your “make the call in 60 seconds” guide:

1. Can you tolerate downtime?

• Yes: Cold migration is on the table and often safest for compatibility edge cases
• No: Use hot migration (Compute vMotion and/or Storage vMotion)

2. Do you need to change the datastore too?

• No: Compute vMotion (host change)
• Yes: Storage vMotion (datastore change) or combined migration

3. Are the hosts compatible (CPU features/EVC alignment)?

• Compatible: Hot migration likely works
• Not compatible or different architectures: Often cold migration or a broader migration approach

4. Is this within the same vCenter, or across vCenters/sites?

• Same vCenter/cluster: Standard migration options
• Across vCenters: Cross-vCenter migration requirements can apply and may involve additional constraints

Pre-flight checklist: what to confirm before you click “Migrate”

If you want migrations that feel boring (that’s the goal), run this checklist.

Compatibility and placement

• Confirm the destination host is healthy and has capacity (CPU, RAM headroom)
• Confirm CPU/EVC compatibility across hosts if doing hot migration (a frequent blocker)
• Ensure required networks/port groups exist on the destination host (labels, VLANs, policies where applicable)

Storage readiness

• For Storage vMotion: validate datastore health, free space, and performance headroom
• Snapshot chains and heavy IO workloads increase migration time and the chance of stalls

Network readiness (especially for vMotion)

• Ensure a VMkernel interface is configured for vMotion on each ESXi host and routed correctly
• Bandwidth matters: VMware’s vMotion networking guidance notes at least about 250 Mbps of dedicated bandwidth per concurrent vMotion session, with higher bandwidth improving performance for larger VMs

Operational hygiene

• Confirm monitoring and rollback plan: what you’ll check after, and what triggers rollback
• If you’re doing this at scale, pair migrations with capacity discipline. Many teams formalize this through structured planning, like the approach described in Accrets’ guide on IT infrastructure capacity planning

Which network is used? vMotion vs provisioning vs management

This is one of the most misunderstood parts of hot and cold migration in VMware.

• Compute vMotion traffic is expected to flow through the VMkernel interface that has vMotion enabled
• Some file copy or provisioning-related operations associated with migrations can involve other pathways depending on configuration, which is why some admins see unexpected utilization on management networks

Practical takeaway

• If your vMotion network is configured correctly, most live migration traffic should not saturate your management network
• If you see unexpected management network utilization during migration windows, review VMkernel service bindings and confirm you’re using the intended migration method and option

For global teams operating across regions with a Singapore hub, network design and security posture are not optional. If you want a Singapore-first multi-cloud security viewpoint to pair with workload mobility, Accrets’ playbook on infrastructure security in cloud computing is a useful companion read.

Step-by-step: how to perform a hot migration (vMotion) in vCenter

This is the common “move a VM with minimal downtime” flow.

1. In vCenter, locate the VM, right-click, then select Migrate
2. Choose your migration type:

• Change compute resource only (move to another host)
• Change storage only (Storage vMotion)
• Change both compute resource and storage (if applicable in your environment)

3. Follow the wizard:

• Select destination host/cluster or datastore
• Review compatibility checks and resolve issues before proceeding
• Choose network mapping if prompted

4. Monitor the task and platform signals:

• Watch migration progress
• Keep an eye on latency and packet drops if you suspect network stress

5. When complete, perform post-migration validation

Expert tip: do your first migrations on a low-risk VM to validate your vMotion VMkernel configuration and bandwidth assumptions, then scale.

Step-by-step: how to perform a cold migration

Cold migration is straightforward but operationally sensitive because it involves downtime.

1. Plan the outage window: coordinate with app owners, define success checks, and confirm rollback authority
2. Gracefully shut down the VM (or suspend, if that’s your method). Cold migration applies to powered-off or suspended VMs
3. In vCenter, right-click the VM and select Migrate (or use your environment’s standard cold migration procedure)
4. Choose whether you’re changing host, datastore, or both
5. Complete the migration, then power the VM back on
6. Run validation checks

When cold migration is the right call

• CPU architectures differ (for example, Intel vs AMD scenarios can block hot migration in some environments)
• You’re making disruptive infrastructure changes and prefer a clean restart to reduce unknowns

Post-migration validation: what experienced admins check immediately

Right after a migration (hot or cold), don’t stop at the “green check.” Verify:

• Connectivity: the VM can reach required networks, and routes/firewall rules behave as expected
• Identity: expected IP/MAC behavior remains consistent with your design
• Storage health: disk latency is normal, datastore IO is stable
• Application checks: services are running, logs are clean, and a basic synthetic transaction passes
• Performance baseline: quick glance at contention indicators (CPU ready, memory pressure, disk latency)

This validation routine is often what prevents small post-migration issues from turning into bigger incidents later.

Troubleshooting: common blockers and quick fixes

CPU/EVC mismatch

Symptoms

• vCenter reports incompatibility, or the migration is blocked with CPU feature warnings

Fix mindset

• Align CPU compatibility where possible (EVC alignment is common), or use cold migration when alignment isn’t realistic

vMotion network misconfiguration or insufficient bandwidth

Symptoms

• Migration fails quickly, is extremely slow, or traffic appears where you don’t expect it

Checks

• VMkernel interfaces: confirm vMotion is enabled where it should be
• Bandwidth planning: avoid stacking too many concurrent migrations on insufficient links. VMware’s guidance highlights per-session bandwidth expectations and why higher bandwidth improves results

Port group or network mapping mismatch

Symptoms

• Migration completes but the VM loses connectivity, or the wizard flags missing networks

Fix

• Ensure the destination host has the same required port groups and policies, and treat this as a pre-flight requirement rather than a post-failure discovery

Storage vMotion stalls or takes too long

Symptoms

• Long-running tasks, slow progress, high IO latency

Likely causes

• Snapshot chains, storage contention, insufficient throughput

Fix

• Schedule heavy storage moves during calmer windows, reduce concurrent Storage vMotions, and validate datastore performance headroom

Cross-vCenter or cross-site constraints

Symptoms

• Migration option unavailable, unexpected requirements, version/licensing warnings

Fix mindset

• Cross-vCenter migrations have specific requirements and constraints. Treat this as a separate project tier, not “just another vMotion”

When hot and cold migration isn’t enough: cross-site moves, compliance, and resilience planning

If you’re moving workloads across regions, data centers, or hybrid environments, you’re no longer just migrating a VM. You’re also answering:

• Where should the workload live for best latency to users?
• What compliance posture is required (data residency, encryption, auditability)?
• How do backup and disaster recovery behave after the move?

For global teams using Singapore as a regional hub, these questions show up fast when balancing performance and compliance across Southeast Asia. If you want a practical lens on speed, cost, and compliance tradeoffs, Accrets’ Singapore cloud VPS field guide for US buyers is helpful background.

If resilience is part of the requirement, pair migration planning with a DR mindset. This guide on cloud computing service providers in Singapore for backup and disaster recovery can help frame what “good” looks like beyond a successful move. If you’re comparing facility tiers, these references on tier 3 data center definitions and tier 4 data centers support a more informed resiliency discussion.

VMware strategy note: if you’re re-evaluating VMware long-term

Sometimes “hot vs cold migration” questions sit inside a bigger strategy conversation: platform standardization, cost shifts, governance, or modernization plans. If that’s you, Accrets’ overview of VMware alternatives is a practical way to understand what options exist without forcing a decision before you stabilize your current operations.

How Accrets can help (brief, practical, and late)

If your migration stays inside a single vCenter and compatibility is clean, you may only need disciplined execution. But if the project includes hybrid cloud architecture, cross-site connectivity, DR design, or a platform transition, it’s often cheaper and safer to get expert eyes on the plan before cutover.

Accrets supports organizations that need migrations to work in real-world constraints, especially when requirements include governance, connectivity, or regional hosting decisions. For teams exploring a broader exit strategy, Accrets offers an OpenStack migration path to escape VMware lock-in when the business case supports it. If ongoing operations is part of the challenge, you can also review Accrets as a managed cloud service provider to see how teams pair migration execution with long-term operational support.

Free consultation: talk to an Accrets Cloud Expert about hot vs cold migration in VMware

If you’d like a second opinion on your migration plan, whether it’s a straightforward vMotion readiness check or a cross-site program, fill out the form for a free consultation with an Accrets Cloud Expert using this contact page.

Dandy Pradana

Dandy Pradana is an Digital Marketer and tech enthusiast focused on driving digital growth through smart infrastructure and automation. Aligned with Accrets’ mission, he bridges marketing strategy and cloud technology to help businesses scale securely and efficiently.