VMware broke CBT mechanism for backing up virtual machines

    As it became known from KB ( 2090639 ) in VMware ESXi hypervisors of versions starting from 4.x and up to date when the QueryChangedDiskAreas team calls to request information about the occupied disk sectors of virtual disks, the return value may be incorrect or be absent altogether. At risk are all VMs whose vmdk disk size exceeds was less than 128 GB and subsequently increased. What it is fraught with - all backup utilities that use this mechanism (for example Veeam) can create invalid backups . The workaround is to disable and re-enable the CBT mechanism for all virtual machines.
    For up-to-date information on a topic, subscribe to the KB listed at the beginning.

    PS in the Veeam newsletter there is a link to the PowerShell script to disable CBT on all virtual machines.

    What is CBT: Changed Block Tracking (CBT) is a VMware feature that helps perform incremental backups. VMware Data Recovery uses this technology and so can developers of backup and recovery software.

    upd: As specified author vzbudorazhevshey all mailing TheRealGostev - at risk are only the VM, in which after the CBT was increased disk size and the increase in the process made the size of the disc "step over» 128GB

    upd2: TheRealGostev continues to investigate the issue and publish new data and clarifications

    Check your virtual machines backups!

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