In VMware environments image-based backups are the most common nowadays; they save directly VMDK blocks instead of having agents installed inside the Guest OS to save single files. Using CBT technology, first introduced with vSphere 4.0, we can now identify only those blocks that changed since the previous backup, and save only those. This allows incremental backups using low disk space and short backup times.

CBT technology and its interaction with Guest OS filesystem however has some issues regarding the optimization for backup purposes. Let’s see an example: we have a Windows 2008 R2 VM acting as a file server. Its More >