Forum Discussion

AndriiPushkarov's avatar
5 years ago

Block-level incremental backup

Hi all, 

Veritas informs. Backup of entire virtual machine, with full schedule: backs up only the blocks that have changed since the .vmdk was created.

Conslusion:  if the virtual machine completely is lost, it is impossible to restore from full backup with the Enable option “Block-level incremental backup”. Is this the right conclusion?

I have the opposite result. 1) I delete the virtual machine.  2) I successfully restore a virtual machine from full backup. Guest OS Linux. “Block-level incremental backup is enabled.

Please explain.


Document Link:



8 Replies

  • This :

    "Backs up only the blocks that have changed since the .vmdk was created. Note that the blocks that are not initialized are excluded from the backup." principally trying to get across the point that even with thick vmdk that only the used blocks are backed-up. IMO, this part "only the blocks that have changed since the .vmdk was created" will always mean that the first full backup is a full backup and so does backup eveything and so will always be able to recover a VM, because it really does include everything since the VMDK was  created.

    • Further to SDO's reply. 

      IMHO the wording poorly describes the process.
      For acellerator backups of VMware, the first backup taken (whether full or incremental) will backup the entire vmdk files (excluding emtpy and deleted space). It will also enable CBT on the VMware side if this is not already done. 
      It will also (and this is the important bit) create a track file for the VM which contains the CBT state at the time of the backup.
      When the next backup is taken, this track file used together with the CBT in VMware to determine which blocks have changed since the last backup (either full or incremental). 

      If you still have your backup logs from the test you performed, you should notice in the detailed job status for the first backup a line just after one saying "info bpbrm (pid=273179) accelerator enabled", that "Info bpbrm(pid=6192) There is no complete backup image match with track journal, a regular full backup will be performed".
      For subsequent backups you will only see the first entry.


      • AndriiPushkarov's avatar
        Level 4

        Clarification. In this case, I use the parameters

        Attributes: “Use Acceleraror” = NO

        VMware: “Enable block-level incremental backup” = YES

        “Enable block-level incremental backup” is needed to feature be able to restore a VM from an incremental backup.