QueryChangedDiskAreas API returns incorrect sectors after extending virtual machine VMDK file with Changed Block Tracking (CBT) enabled in ESXi 8.0u2

Products

• VMware vSphere ESXi

Issue/Introduction

CBT's QueryChangedDiskAreas may lose some data changed on the disk after disk is hot-extended.
It happens on ESXi 8.0u2 and VMC 1.24.1

Environment

VMware vSphere ESXi 8.0.2

Cause

There is a bug in the QueryChangedDisk Areas API.

Resolution

In order to resolve this issue, update to ESXi 8.0 Update 2b or newer.

Workaround:
1. Reset CBT after disk is hot-extended. Then, take a full backup immediately.
It does not fix existing backups, but it makes sure the new ones are good. Follow these steps to reset CBT Resetting Changed Block Tracking for VMware vSphere virtual machines
2. Or, user extend disk in offline.