Veeam Backup and VMware ESXi 6 CBT issue
Last week an issue was discovered within VMware ESXi 6 where by Change Block Tracking (CBT) can return incorrect changed blocks . This means you will end up with inconsistent incremental backups.
VMware have released a KB article (KB2136854) which illustrates the problem and further goes on to say that there is no current patch or fix, however there are some work arounds:
- Downgrade to vSphere 5.5
- Shut down the Virtual Machine before starting your backup
- Use full backups instead of incrementals
To me none of these work arounds are really an option for many organizations
The team over at Veeam have been testing the CBT issue with ESXi 6 and have come up with a fourth option which is to disable Change Block Tracking within the advanced settings of the backup job (full, incremental backups and replica jobs). Veeam go onto explain that disabling CBT in the backup job is essential or your backups could contain corruption.
The official Veeam forum thread for this issue can be found by clicking here – There’s a new CBT bug in ESXi 6