The Replication Process Slows Down After CBT Reset

Product version: 10.1

Last modified: 10 September 2020


How is the replication process performed after the CBT reset and why is it much slower?


NAKIVO Backup & Replication uses the VMware CBT technology to identify which data blocks have been changed since the last job run. Sometimes, CBT can be reset for such reasons as power outage, network issues, etc. When CBT reset occurs, NAKIVO Backup & Replication performs incremental backups using the NAKIVO proprietary change tracking technology which requires reading the entire contents of all VM disks. Therefore, the initial job run after CBT reset takes longer to complete than a regular, consequent job run. The replication process is performed in the following way:

  1. The target Transporter reads replica VM's disks and builds the base/differential files.
  2. The Director then downloads the base files to the Director location and uploads them to the source Transporter. In case that the source and target Transporter are the same service, the solution checks if the base files exist and are up-to-date, and uploads them if needed.
  3. The source Transporter then uses the base files to transfer the changed blocks of data to the target Transporter. This process requires NAKIVO Backup & Replication to read all the source VM snapshot disks.

After the successful initial replication job run, all consequent job runs are performed significantly faster.