Preflight Assessment

Overview

Preflight assessment runs a set of read-only checks against a discovered workload and returns a compatibility verdict before you submit a migration job. The goal is to catch the issues that would cause a migration to fail or a post-migration boot problem — OS not supported, firmware mismatch, disk layout too complex — while you still have time to fix them on the source.

Prerequisites

A successful discovery scan for the source environment
Credentials on the registered source with read access to VM configuration and disk metadata

Run Preflight

Dashboard
CLI

Select candidate workloads

In Migration → Discover, tick the VMs you plan to migrate and click Preflight Selected. You can preflight a single VM or an entire wave.

Start the assessment

XMS inspects each VM through the vSphere API and applies the Xloud compatibility ruleset. The scan is read-only and completes in seconds for most workloads.

Review the verdict

Each VM receives one of three outcomes:

Verdict	Meaning
Pass	All checks passed — safe to migrate
Warn	Migration can proceed but with caveats — review the warnings
Block	One or more checks failed — resolve before submitting a migration

Expand a row to see every individual check, its status, and the suggested remediation.

All target workloads reach Pass or Warn before you submit a migration.

# Run preflight against one or more VMs
xms preflight run --source prod-vcenter --vm win-ser-2022

# Preflight an entire wave from a file
xms preflight run --source prod-vcenter --from-file wave-1.txt

# Fetch the latest verdict
xms preflight show --source prod-vcenter --vm win-ser-2022

Check Categories

Preflight runs checks across five categories. Each category produces one or more individual checks that roll up into a category score.

Compute

Check	Description
Firmware type	BIOS and UEFI are both supported. Secure Boot state is recorded for post-migration validation.
Hardware version	vSphere hardware versions are checked against the supported range for the installed disk transport libraries.
Guest OS family	The reported guest OS is matched against the supported Xloud guest catalog.
Resource shape	vCPU count and memory are sanity-checked against project quotas in the target Xloud project.

Storage

Check	Description
Disk count and size	Total disk size is compared to available quota and to the target volume type’s maximum size.
Disk layout	Complex layouts (raw device mappings, shared disks, independent disks) are flagged. Standard thin and thick disks are supported.
Snapshot state	Active snapshots at migration time may slow down export. XMS flags VMs with long snapshot chains.

Network

Check	Description
Adapter count	Each source adapter must map to a target Xloud network.
Port group names	Port group names are captured for the later network mapping step.
MAC preservation	The option to preserve MACs is flagged as informational — a network mapping with conflicting MACs will be rejected at submit time.

Guest

Check	Description
Driver readiness	The OS is matched against the VirtIO driver set that will be injected during guest conversion.
Boot loader	GRUB (Linux) and the Windows BCD are confirmed present. Missing boot loaders are a hard block.
Filesystem type	Supported filesystems include ext2/3/4, XFS, Btrfs, NTFS, FAT32, ReFS, and LVM with these underlying types.

Protection

Check	Description
CBT enabled	Warm migration requires Changed Block Tracking. XMS surfaces this as a warning and offers to enable it in-place.
Snapshot support	Warm migration needs the ability to take a snapshot at sync start. Hosts with disabled snapshot support are blocked from warm.

Common Blockers and Remediation

Blocker	Root Cause	Fix
Unsupported guest OS	The guest ID returned by vSphere does not match the Xloud guest catalog	Upgrade or reinstall the guest OS to a supported version before migrating
Raw Device Mappings	A disk is mapped directly to a LUN on the source	Convert the RDM to a VMFS-backed disk before migration
Shared disks	Two VMs share the same VMDK	Un-share or take an online copy before migration
CBT not enabled (warm)	Change tracking has never been turned on	Enable CBT from preflight — XMS will write the config change through the vSphere API
Missing boot loader	Damaged GRUB or BCD	Repair the boot loader on the source first; migration cannot recover a broken boot loader

Most warnings are safe to ignore for a first pass. Focus on blockers and come back to the warnings if a post-migration boot issue appears.

Preflight vs Runtime Checks

Preflight is a read-only prediction. XMS still performs runtime validation at every stage of the migration pipeline — disk reads, transport negotiation, guest conversion, and volume finalize each have their own checks. A preflight pass does not guarantee a successful migration, but a preflight block does guarantee a migration would fail.

Next Steps

Cold Migration

Run a single-pass migration against a powered-off workload

Warm Migration

Start a continuous sync against a running workload

Troubleshooting

Diagnose preflight blockers and discovery errors

Core Services

Other Services

Preflight Assessment

Overview

Run Preflight

Select candidate workloads

Start the assessment

Review the verdict

Check Categories

Compute

Storage

Network

Guest

Protection

Common Blockers and Remediation

Preflight vs Runtime Checks

Next Steps

Cold Migration

Warm Migration

Troubleshooting

​Overview

​Run Preflight

Select candidate workloads

Start the assessment

Review the verdict

​Check Categories

​Compute

​Storage

​Network

​Guest

​Protection

​Common Blockers and Remediation

​Preflight vs Runtime Checks

​Next Steps

Cold Migration

Warm Migration

Troubleshooting

Overview

Run Preflight

Check Categories

Compute

Storage

Network

Guest

Protection

Common Blockers and Remediation

Preflight vs Runtime Checks

Next Steps