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Backup Modes

There are two backup modes available for VMware virtual machine backup:

  • Non-VDDK backup mode
  • VDDK backup mode

For VDDK backup mode, CloudBacko Go must be installed on a supported Windows operating system platform.

Non-VDDK Backup Mode

For VM on free version of VMware hosts, backup is performed in non-VDDK mode. Backup in non-VDDK mode produces a backup chain that consists of a full file and a set of delta files:

  • During the first backup, full files (e.g. virtual disk file (*.vmdk)) are created in the backup destination.
  • During subsequent backup, In-file delta, the block-level incremental/differential backup feature of CloudBacko Go is employed, to track only data blocks that have change since the last backup. All changed data blocks are saved as incremental / differential delta files in the backup chain.

During a subsequent backup in non-VDDK mode, VM files are streamed to CloudBacko Go for delta generation:

Pros Free version of ESXi is supported.
Cons Slower backup speed for subsequent backup compared to VDDK backup, as a result of having the entire VM backed up every time regardless of the actual used size.

VDDK Backup Mode

For VM on VMware host on Enterprise Standard, Enterprise and Enterprise Plus Edition, backup is performed in VDDK mode. Backup in VDDK mode produces a backup chain that consists of a full VDDK file and a set of VDDK incremental files.

  • During the first backup, full files (*.F.vddk) are created in the backup destination.
  • During subsequent backup, Changed Block Tracking (CBT) - a VMware native feature (https://kb.vmware.com/kb/1020128) is employed, to identify disk sectors altered since the last backup. Altered blocks are saved as incremental VDDK file (*.I.vddk) in the backup chain.

During a subsequent backup in VDDK mode, CloudBacko Go queries CBT through VADP (vSphere APIs for Data Protection) to request for transmission of all altered blocks since the last backup.

As there is no need to stream the VM files through CloudBacko Go for delta generation, backup in VDDK mode will greatly enhance the speed of subsequent backup.

Pros Faster backup speed for subsequent backups compared to non-VDDK backup, as a result of backing up only the used size of your VM instead of the entire machine to enhance backup efficiency. This also helps with minimizing the storage size requirement and saving storage cost.
Cons Require paid license, i.e. VMware Essentials License for usage of vSphere API.

Comparison between VDDK and Non-VDDK Modes

VDDK (CBT) Non-VDDK
Full Backup Used data size of guest Provisioned data size of guest
Incremental / Differential Generated by VMware Host using CBT Generated by CloudBacko Go on the staging machine using in-file delta
Storage Size Uses less storage quota Uses more storage quota
Storage Cost Lower storage cost Higher storage cost
Backup Speed Faster backup speed due to smaller data size Slower backup speed due to larger data size
Run Direct Support YES NO
Restore from VDDK to VMDK format YES NO
Granular Restore YES YES
CloudBacko Go on Windows Platform YES YES
CloudBacko Go on Non Windows Platform NO YES
public/documentation/vmware/backup_mode.txt · Last modified: 2021/07/14 16:40 by ronnie.chan