VMware storage migration is the process of moving a VM’s files from one datastore to another without breaking service expectations. In practice, it usually means choosing between Storage vMotion (online), cold migration (planned downtime), a no-Storage-vMotion workaround, or a platform shift such as VMFS5 to VMFS6 or vSAN. This guide gives you the decision tree, pre-checks, and failure-mode playbook to migrate with confidence. Read on, because the details you validate before and after the move are what prevent the painful surprises.
TL;DR Decision Tree: Choose the Right Migration Method in 60 Seconds
Answer these four questions and you’ll know which path to take.
1) Do you need zero or near-zero downtime?
- Yes: Aim for Storage vMotion (online migration) if your licensing and workload constraints allow it.
- No: Cold migration (power off, move, power on) is usually the most predictable.
2) Do you have Storage vMotion available in your vSphere licensing?
- Yes: Your “default safe” is Storage vMotion for storage-only moves.
- No or not sure: You still have safe options such as cold migration, clone or copy-based moves, or backup and restore cutover. Some environments run into this due to licensing constraints.
3) Any workload blockers?
These often force downtime or alternative methods:
- Shared-disk clustering or multi-writer scenarios
- Snapshot consolidation issues
- Datastore visibility mismatches across hosts
4) What are you really migrating?
- Storage only: Move VM files to another datastore
- Compute and storage: Move host or cluster and datastore
- Datastore modernization: VMFS5 to VMFS6 evacuation
- Platform shift: To vSAN, to hybrid cloud, or away from VMware
Before You Move Anything: Pre-Migration Checklist That Prevents Most Failures
Most migration failures are predictable outcomes of skipping pre-checks. Use this checklist to create a clean go or no-go decision.
Environment checks
- Datastore free space: Ensure the target has enough capacity, including buffer for snapshot growth.
- Snapshot health: Consolidate if needed; deep snapshot chains can inflate migration time and risk.
- Host connectivity: Confirm every host that might touch the VM can see the target datastore.
- Storage path health: A degraded path can turn a short job into hours.
- Policy and compatibility: If you use storage policies, confirm the target datastore meets them before migration.
- Change window and rollback: Define what “abort” looks like and what you’ll do if performance degrades.
If you’re doing this at scale or under governance requirements, it helps to treat storage migration as part of a broader operational discipline like capacity planning and service readiness. Accrets’ guide on IT infrastructure capacity planning aligns well with this runbook mindset.
Risk controls
- Batching plan: Start with lower-risk, lower-I/O workloads before moving the most critical systems.
- Success criteria: “VM powered on” is not enough; define post-migration validation.
- Communication plan: Stakeholders, timing, and who decides to pause or roll back.
Method 1: Storage vMotion (Online Datastore Migration With Minimal Downtime)
If you can use Storage vMotion, it’s often the cleanest way to move a VM’s storage while keeping services up. It’s commonly used for maintenance, storage refreshes, and rebalancing.
When to use Storage vMotion
- You need to migrate with minimal downtime
- You’re moving from one shared datastore to another
- Your workload does not have known blockers such as shared clustering disks or special disk settings
How it typically works operationally
In vSphere you generally choose one of these flows:
- Change storage only: Same host or cluster, new datastore
- Change compute resource and storage: New host or cluster and new datastore
Watch the constraints that make migrations unexpectedly painful:
- Migration concurrency: Too many concurrent migrations can saturate storage and network.
- Stun sensitivity: Latency spikes and high change rates can increase service impact.
If you need to align migration decisions with broader infrastructure strategy discussions, especially when stakeholders mix up storage and cloud terms, Accrets’ overview on the difference between cloud computing and cloud storage can help set expectations.
Method 2: Cold Migration (Planned Downtime, Highest Predictability)
Cold migration is often the most predictable option when you have a controlled downtime window or workload blockers that complicate online migration.
When cold migration is the right answer
- You have shared disks or clustering constraints
- Your licensing does not support Storage vMotion
- You want maximum control and a straightforward rollback story
High-level runbook
- Schedule downtime and confirm approvals.
- Power off the VM and confirm it is truly quiesced.
- Move VM files to the target datastore.
- Power on and validate the platform and application behavior.
Method 3: No Storage vMotion? Three Safe Paths for Tight Licensing Scenarios
When Storage vMotion is not available, you can still migrate safely with a structured approach.
Path A: Compute and storage move workflow
If your environment supports a workflow that combines compute and storage change, treat it like any other migration with pre-checks, batching, and validation.
Path B: Clone or copy-based move with cutover
This approach is useful when you want a clean rollback because the original VM can remain intact until you cut over.
- Best when you can accept downtime at cutover
- Useful when you want a parallel build approach
Path C: Backup and restore or replication cutover
If you already run a mature backup or replication process, storage migration can become a controlled restore and cutover event.
- Strong fit for auditable environments
- Clear rollback plan
- Enables validation before switching traffic
If your organization is tying migration projects to resilience targets, Accrets’ guide to backup and disaster recovery considerations for cloud service providers in Singapore is a relevant companion.
Special Case: VMFS5 to VMFS6 Datastore Migration (Evacuate, Recreate, Validate)
Many teams run into VMFS modernization during storage refresh cycles. Operationally, VMFS5 to VMFS6 is often handled as an evacuation and migration exercise.
Operator runbook
- Confirm platform readiness and shared visibility across hosts.
- Evacuate workloads from VMFS5 using Storage vMotion where possible or cold migration where required.
- Create the VMFS6 datastore.
- Move workloads onto VMFS6.
- Validate and document the change.
This is where hidden dependencies commonly appear, especially around datastore visibility, host readiness, and policy compliance. Go or no-go gates reduce risk more than any single tool.
Common Blockers and Failure Modes (And What to Do Instead)
Users rarely search for a “best method.” They search for the failure they are experiencing.
Blocker 1: Shared disks, clustering, and multi-writer constraints
Some clustered configurations can prevent online migration or require the VM to be powered off to migrate safely.
- What to do: Plan a cold migration window and validate that you are not breaking shared-disk assumptions.
Blocker 2: Snapshot consolidation problems
Deep snapshot chains and consolidation failures increase risk.
- What to do: Consolidate before migration. If consolidation is risky, use a clone or copy-based approach that reduces operational fragility.
Blocker 3: Migration duration surprises from throughput and concurrency
Migration time is driven by data size, change rate, effective throughput, and how many migrations run concurrently.
- What to do:
- Batch migrations
- Avoid peak I/O windows
- Pause when latency exceeds agreed thresholds
Blocker 4: Compatibility and policy errors
Target datastores might not meet storage policy requirements or might not be visible to the right hosts.
- What to do: Fix datastore visibility and policy alignment first instead of repeating the same failing attempt.
If security and governance are in scope, aligning the migration plan with your cloud security posture can prevent late-stage blockers. Accrets’ cloud security consulting perspective for Southeast Asia provides a useful framework.
Post-Migration Validation: Don’t Declare Victory Until These Checks Pass
A successful storage migration is “application stable and performance normal,” not just “task completed.”
Platform checks
- VM is running on the intended datastore
- Datastore paths are healthy
- No consolidation warnings or unexpected snapshot growth
- Performance is within acceptable baselines
Application checks
- Services are up and stable
- Logs show no storage-related timeouts
- Transaction flows and user experience are normal
Operational hygiene
- Update documentation and CMDB
- Record change notes including approvals and timing
- Capture lessons learned for the next migration wave
When Storage Migration Is Actually a Bigger Strategy Decision
Sometimes the right question isn’t “How do we migrate this datastore?” It’s “What are we migrating toward?”
Moving to vSAN
This can be a platform shift rather than a routine move. Expect planning around network throughput, operational patterns, and rollout sequencing.
Operating across regions
For global teams, Singapore is often a strategic location for latency, compliance, and regional access. If your migration is part of a larger footprint decision, Accrets’ perspective on why U.S. companies choose Singapore data centers in Southeast Asia and its guide to hybrid cloud providers in Singapore for U.S.-based teams can help frame the location and architecture conversation.
Considering VMware alternatives
A storage migration project often becomes the moment leadership asks whether long-term VMware dependency is acceptable. For a structured starting point, see Accrets’ overview of VMware alternatives.
How Accrets Helps Reduce Risk (Planning, Execution, and Long-Term Flexibility)
The biggest reliability improvements usually come from process: readiness checks, batching discipline, validation standards, and a roadmap that matches business constraints.
Accrets can support you across the lifecycle:
- Assessment and runbook design: Method selection, risk controls, and batching plan
- Execution support: Planned change windows, troubleshooting, validation
- Resilience alignment: Backup and DR design, operational governance
- Modernization paths: Hybrid cloud, platform transitions
If your organization is actively working to reduce vendor lock-in, you may want to review Accrets’ approach to escaping VMware lock-in with an OpenStack migration strategy.
Free Consultation
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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.
