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QueryChangedDiskAreas API with changeId set to "*" throws FileFault error (1033816)

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When using QueryChangedDiskAreas with changeId set to "*" to gather information about snapshots, you see a FileFault error if changed block tracking (CBT) is enabled on the virtual machine with existing snapshots:

Cannot compute changes for disk /vmfs/volumes/4b42258a-3c6b0036-85af-0015c5f0ebb5/SUSE 11 64-bit_1/SUSE 11 64-bit_1-000001.vmdk: Unknown change epoch.
[2011-01-26 14:44:00.544 F5610B90 info 'Vmomi'] Throw vim.fault.FileFault.


  1. This issue occurs when CBT is enabled on a virtual machine on which snapshots exist. Snapshots that exist before enabling CBT do not have changeId set and when the QueryChangedDiskAreas API is invoked, it returns a filefault error when it has to return the changeId.
To workaround this issue, enable CBT on a virtual machine that does not have snapshots. When you create a snapshot, disk changes are tracked as CBT is already enabled on the virtual machine.
  1. Create a virtual machine without snapshots. 
  2. Activate CBT. For more information, see Changed Block Tracking (CBT) on virtual machines (1020128).
  3. Create a snapshot.
  4. Call queryChangedDiskAreas with changeId set to "*".

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