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CBT enabled vs disabled

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Forum Member
Posts: 42
Comments: 54

Hi, just wondering if there any idea how much longer to backup a VM when CBT is disabled vs enabled? How does acronis do incremental backup when CBT is disabled? (just trying to understand the concept)



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Acronis Program Manager
Posts: 22
Comments: 3670

Hi Aldous,

The time difference between CBT=on and CBT=off depends on multiple factors including the size of the VM disks, the amount of data inside them and the CPU/RAM resources available on the host. With CBT=off Acronis backup calculates the checksums of the range of sectors read during backup and compares it with the checksum of the same sectors range within existing backup (which is being updated incrementally). If the checksums mismatch then this range is considered as changed and is saved into the backup.

With CBT=on there is no need to calculate the checksums of all sectors on the disk - instead there are only sectors ranges reported by CBT (from native hypervisor CBT API or from special CBT driver in case of Hyper-V 2012 or lower) processed .

Thank you.