This was a lesson and learns for me after I recovered the data back. My data was lost and no backup…

I had a virtual machine was moved from ESX 3.0 to ESXi 5.1 host long time ago. The virtual disk size show 0 and I cannot do storage migration and snapshot on the VM due to the hardware version was 3, it’s too low.

Generally I take snapshot before upgrade VM HW version, but that’s impossible on a VM of HW version 3 that running on vCenter Server 5.1. So I upgraded the VMware Tools and then VM hardware version by Update Manager. VMware Tools was successfully upgraded, but VM hardware version upgrading got error.

Then I right clicked the VM and used “Upgrade Hardware Version” option directly, it’s successfully without any prompt…finally I got “A disk read error occurred” when boot up. L

You may think it’s caused by SCSI controller since VM hardware version 3 supports IDE virtual disk and version 9 supports only SCSI virtual disk for best performance. That’s not my case. I tried several way to recover the disk, like convert the VM by convertor, mount the disk to other virtual machine, change SCSI parameter…etc.

I don’t think hardware version upgrading changes real virtual disk too much, it must be something changed on the head section of virtual disk, or description file. After consulted with Microsoft we got it fixed finally.

When I mounted the corrupted disk on other virtual machine, partition and size was recognized correctly. And disk manager also can recognize the NTFS file system. I can saw new drive appear in My Computer as well, but it show me “File or directory corrupted…” when I tried to open the drive. It more like a file system issue… it’s easy, just run following command to check any logical errors:

Chkdsk [drive letter]

Wow….a lot of error and files was listed, then I tried command:

Chkdsk /f [drive letter]

That’s real fix logical issue of disk. I could open the drive after used this command.

I mounted the drive back to the broken VM and powered on. New issue came up…Windows show me “Windows NT could not start because the below file is missing or corrupt: C:WindowsSystem32Ntoskrnl.exe”. I replaced the file but no help. The file was existed in the location, and file size was same like other VM, it’s perhaps not file issue?

Then I open VMDK file, aha….ddb.adapterType = “LegacyESX”, changed it to ddb.adapterType = “lsilogic” according to my SCSI controller set, my lovely Windows Server startup screen came back again. J

Okay, I talked too much. To summarize the fixing steps:

• Mount the broken disk to a good virtual machine with same operating system. ( I’m not sure is it ok to mount on higher version of OS )
• Run chkdsk [drive letter] to check if logical error existing.
• Run chkdsk /f [drive] letter] to fix the logical error.
• Unmounts the disk from good VM.
• Edit the VMDK file in ESXi console.
• Change the value of ddb.adapterType to proper SCSI controller type according to your SCSI controller setting.
• Mount the disk back to broken VM.
• Power on.

Here is my learning from that contingence:

1. vCenter Server does not verify compatibility of VM hardware version during upgrading. Actually it’s not allowed to upgrade VM version from 3 to 9 directly.
2. vCenter Server does not allowed you choose which VM hardware version you want to upgrade to, always latest.
3. If you upgrade VM version from 3 to 9 directly, a SCSI controller will be added to the VM, value of ddb.adapterType will be changed to LegacyESX. You will not able to boot up the VM due to Windows Server 2003 does not contain proper SCSI driver.
4. VM version upgrading looks like changes parameters of VMDK file but don’t change too much of real virtual disk, such as NTFS mapping and MBR table…etc.

Last, you may still face BSOD after use above solution since item 3 above, you have to inject the SCSI driver, please refer to KB 1005208 and KB 1006858.

Last of last…. 🙂 please take a backup of your virtual disk before you do any change!!!!!