Summary
The VMware QueryChangedDiskAreas API returns incorrect sectors after extending a virtual machine VMDK file with Changed Block Tracking (CBT) enabled.
Symptoms
When using backup software that uses the Virtual Disk Development Kit (VDDK) API call QueryChangedDiskAreas() to return a list of allocated disk sectors, the following symptoms occur:
- The list of allocated virtual machine disk sectors returned is incorrect
- Backups appear to be corrupt or missing data
Resolution
This is a known issue affecting VMware ESXi 4.x and ESXi 5.x.
This issue is resolved in:
- ESXi 5.0 Patch 10. To download this patch, go to Download Patches. For more information, see VMware ESXi 5.0, Patch Release ESXi500-201412001 (2088715).
- ESXi 5.1 Update 3, available at VMware Downloads. For more information, see the VMware ESXi 5.1 Update 3 Release Notes.
- ESXi 5.5 Patch 4. To download this patch, go to Download Patches. For more information, see VMware ESXi 5.5, Patch Release ESXi550-201501001 (2099265).
Currently, there is no resolution for ESXi 4.x.
To work around this issue, you must turn CBT off and then on for disks extended beyond 128 GB. You can do this through a vCenter Client on a virtual machine that is shut down.