VDI export to VMDK results in a corrupted disk

[Danp]

@abudef What steps are you performing to export the VDI as a VMDK?

[abudef]

[Danp]

Ah... ok. I think I originally checked the VM export.

This could be a bug. Does it occur with all VDIs? What happens if you try to import the file back into XO?

[abudef]

I tried to export 3 VDIs from 2 different XCP-ng pools. 2 VDIs from Windows Server 2025 VMs and 1 from Windows Server 2022 VM. All 3 VMDKs seem to be corrupted when I try to use them in VMware Workstation.

I also tried reimporting 1 of the exported VMDKs back into the XCP-ng repository and the VM booted without any issue using the reimported VDI.

Maybe there is either an issue with this VMDK format in VMware Workstation or the XO´s export/import method creates VMDK files that can be exported and reimport back into XCP-ng repository while preserving the original state of the VDI in the XCP-ng repository even if it´s unusable in VMware WS.

[abudef]

[Danp]

Have you attempted to analyze the exported file using qemu-img?
For example:

qemu-img info file.vmdk
qemu-img check file.vmdk

[abudef]

qemu-img.exe info Windows Server 2025.vmdk
image: Windows Server 2025.vmdk
file format: vmdk
virtual size: 64G (68719476736 bytes)
disk size: 64G
cluster_size: 65536
Format specific information:
    cid: 2849992906
    parent cid: 4294967295
    create type: streamOptimized
    extents:
        [0]:
            compressed: true
            virtual size: 68719476736
            filename: Windows Server 2025.vmdk
            cluster size: 65536
            format:

qemu-img.exe check Windows Server 2025.vmdk
No errors were found on the image.

It seems that the disk itself is formally OK, but the content is somehow corrupted.

[Danp]

It's possible that the issue lies within VMware Workstation.

[abudef]

I don't think it's a VMware issue. If the XO export created a VMDK with incorrect data block contents, qemu-img check can still complete without reporting any errors. It only means that it did not find any problems with the VMDK structure.

[abudef]

I´m not a developer so I asked Ai what it "thinks" about it...

┌─────────────┐
│  XCP-ng VDI │
└──────┬──────┘
       │
       │ VDI_exportContent()
       │ format = VDI_FORMAT_VHD
       ▼
┌──────────────────┐
│    VHD stream    │
└────────┬─────────┘
         │
         │ vhdToVMDK()
         ▼
┌─────────────────────────┐
│  vhdToVMDKIterator()    │
└───────────┬─────────────┘
            │
            │ parseVhdToBlocks()
            ▼
┌─────────────────────────┐
│    parseVhdStream()     │
│                         │
│    VHD blocks           │
│    { id, data }         │
└───────────┬─────────────┘
            │
            │ onlyBlocks()
            │
            │ lba = id * blockSize
            ▼
══════════════════════════════════════════
     POSSIBLE ERROR HERE
     Incorrect mapping of id ↔ data
     or incorrect block ordering
══════════════════════════════════════════
            │
            ▼
┌─────────────────────────┐
│   generateVmdkData()    │
│                         │
│   VHD block             │
│      ↓                  │
│   grainData             │
│      ↓                  │
│   createMarkedGrain()   │
│      ↓                  │
│   tableBuffer           │
└───────────┬─────────────┘
            │
            ▼
┌──────────────────┐
│   VMDK stream    │
└────────┬─────────┘
         │
         ▼
┌──────────────────┐
│    VMDK file     │
└──────────────────┘