Change Block Tracking (CBT) is supported. It allows backup applications to determine the delta of changes in the virtual machine since last backup and only read and transfer those changes when doing the next backup incrementally. Data Manager uses one or more virtual machine proxies for reading and transferring virtual machines’ disk changes.
Any L0 backup of a virtual machine reads the entire contents of all disks and writes the same to storage using DD Boost (leveraging global deduplication). Any non-L0 backup of a CBT-enabled virtual machine will only read changes in the disks from the last backup. It will overlay those changes on a copy of the last backup to generate a new full backup (while moving only incremental changes).
Backup files are written to storage using fixed size segments (FSS) of 8K. Backup files on storage are always thick. For example, VMDK file-size on storage is equal to the size of provisioned disk.
