"Unable to create dummy disk, A general system error occurred: Invalid argument" During HCX Migration

Products

• VMware HCX

Issue/Introduction

When performing migrations using VMware HCX, the following error can appear during the storage reservation phase

"Unable to create dummy disk, A general system error occurred: Invalid argument"

This error below can be seen in the migration view when the bulk migration fails

 

This error prevents the migration from proceeding and appears in the HCX migration status. Common observations include

• Migration task failure specifically during the storage reservation phase
• Consistent errors for specific VMs being migrated
• Same error occurring on subsequent retry attempts

Environment

VMware HCX

Cause

The error occurs when leftover VM folders (folders for a virtual machine but with no virtual machine within it) exist on the target host datastore from previous migration attempts. These residual folders interfere with HCX's storage reservation process, preventing the creation of required temporary dummy disks used for verification.

Resolution

Follow these steps to resolve the error

1. Access the Target Environment
   • Log into the vSphere Client
   • Navigate to the Storage view
   • Locate the target datastore where VMs are being migrated
2. Clean Up Stale Folders
   • Browse the datastore contents
   • Locate folders with names matching the migrating VMs
   • Remove any stale folders associated with the failed migration attempts
   • Verify complete removal of all temporary files and folders
3. Retry the Migration
   • Return to the HCX interface
   • Cancel any existing failed migration tasks
   • Create a new migration job for the affected VMs
   • Monitor the storage reservation phase to confirm successful completion

If the error persists after following these steps, contact Broadcom Support for further assistance.

Please provide the below information when opening a support request with Broadcom for this issue

• Migration details (VM Name, Migration id, Screenshot of error as seen via UI)
• Source and Target HCX log bundles with HCX database dumps and IX appliance selected.