VMware acknowledged a known issue (KB2136854) within ESXi 6.0 and 6.0 U1. CBT looses the information of I/Os during snapshot consolidation. The main backup isn’t affected but all data written during the consolidation task are missed.
ALL CBT incremental backups are potentially affected.
VMware currently has no resolution.
VMware released a patch for the CBT bug.
Possible workarounds before intall the patch are:
- Downgrade to ESXi version 5.5 and (if necessary) downgrade the VM HW version from 11 to 10.
Reverting to a previous version of ESXi (KB1033604)
Downgrading the virtual machine hardware version in ESX/ESXi (KB1028019)
If you are using Veeam for your backups, you can disable the CBT feature to remain consistent.
- Edit Backup Job
- Select Storage
- Click on Advanced button
- Go to vSphere tab and deselect Use changed block tracking data (recommended) and click on OK then Finish.