Changed Block Tracking (CBT) Bug fixed for ESXi 5.0 and ESXi 5.1

Good News if you use ESXi 5.0 or ESXi 5.1 – the CBT Bug is fixed for these versions.

Unfortunately there is no fix available at the moment for ESXi 4.x and 5.5.

If you do not know about this issue you can read my previous post or VMware KB 2090639: QueryChangedDiskAreas API returns incorrect sectors after extending virtual machine vmdk file with Changed Block Tracking (CBT) enabled

Here you can find the patch for

If you use ESXi 4.0 or 5.5 you can only use the following workarounds for the issue:

  • perform a Storage vMotion after having extended the CBT-enabled disks past a 128 GB boundary
  • or you disable and re-enable CBT after extending past the boundary:
  1. turn off CBT
  2. take a snapshot
  3. delete the snapshot
  4. turn on CBT
  5. take one more snapshot
  6. last but not least delete the snapshot


1 Comment

  1. Chris

    according to vmware support there is a fix available for ESXi 5.5 (

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