Understanding VMware Backup Mode
Non-VDDK Backup Mode End of Support
Starting with AhsayOBM v9 or above, Non-VDDK backup mode is no longer supported in VMware backups and ONLY VDDK backup mode is supported.
Therefore, FILE mode is also no longer supported in VMware Backup set type.
VMware backup sets created in AhsayOBM v8.5.4.x with AhsayCBS v9 can still be run in nonVDDK backup mode. However, if the AhsayOBM v8.5.4.x is upgraded to AhsayOBM v9 or above with AhsayCBS v9, VMware backup sets in non-VDDK backup mode will fail to back up.
Therefore, if the VMware backup set will continue to run backup jobs in non-VDDK backup mode, it is recommended to NOT upgrade to AhsayOBM v9 and continue using AhsayOBM v8.5.4.x.
For more details, refer to the following article:
FAQ: VMware Non-VDDK Backup Mode in AhsayOBM v9
VMware Backup Mode
The backup mode is chosen by AhsayOBM at the start of a backup according to the license key on the VMware host, the operating system of the backup machine where the AhsayOBM is installed, as well as other requirements outlined in the Requirements section.
For VDDK backup mode, AhsayOBM must be installed on a supported Windows operating system platform.
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 (Changed Block Tracking (CBT) on virtual machines) 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, AhsayOBM 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 to the Backup Client Computer in the Requirements section for delta generation, backup in VDDK mode will greatly enhance the speed of subsequent backups.
| Pros | Faster backup speed for subsequent backups, 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. Run Direct is supported. |
|---|---|
| Cons | Requires paid license, i.e. VMware Essentials License for usage of vSphere API. Requires VMFS5, VMFS6 or vSAN datastores to support full and incremental backups according to used size of the guest VM. |
In VDDK backup mode, if the guest VM is located on an NFS datastore, the full backup will be performed using provisioned size of the guest VM.
Further to the VMware license requirement described above, there are other requirements for VMware VM backup in VDDK backup mode. Refer to the Requirements section for details.
Features of VDDK Backup mode
| VDDK (CBT) | |
|---|---|
| Full Backup | Use data size of guest |
| Incremental/Differential | Generated by VMware Host using CBT |
| Storage Size | Uses less storage quota |
| Storage Cost | Lower storage cost |
| Backup Speed | Faster backup speed due to smaller data size |
| Run Direct Support | YES |
| Restore from VDDK to VMDK format | YES |
| Granular Restore | YES |
| AhsayOBM on Windows Platform | YES |
| AhsayOBM on Non-Windows Platform | NO |
| Backup and Restore to vSAN Cluster | YES |
VDDK Backup Mode Limitations
Guest VMs with RDM (Raw Device Mapping) disks, or iSCSI initiator are not supported. As VMware is not able to create a snapshot of raw, RDM disks or iSCSI disks.
Although guest VM level backups are not possible, it is recommended to install AhsayOBM directly onto the guest VM to perform backups.
Guest VMs with raw disks are not supported. As VMware is not able to create a snapshot of raw disks.
To perform a backup of the guest VM, it must either be powered off before the backup job or alternatively install AhsayOBM directly onto the guest VM to perform backups.
- Backup of guest VM snapshots are not supported.
- Backup of guest VM state (e.g. power on state / suspend state) is not supported.
- If a guest VM has virtual hard disks larger than 2 TB, VMware snapshot operations can take much longer to finish, therefore backups may take longer.
Guest VMs setup with PCI vSphere DirectPath I/O devices are not supported. As VMware is not able to create a snapshot of these devices.
The guest VMs must be powered off before a backup can be made.
All independent disks both persistent and non-persistent are not supported. As VMware does not support snapshots of independent disks when the guest VM is powered on.
To perform a backup of the guest VM, it must either be powered off before the backup job or alternatively install AhsayOBM directly onto the guest VM to perform backups.
Backup of suspended guest VMs with independent disks are also not supported.
Guest VMs configured with bus sharing are not supported. As VMware does not support snapshots of this type of configuration.
Although guest VM level backups are not possible, it is recommended to install AhsayOBM directly onto the guest VM to perform backups.
VDDK API Changes
VDDK 7 API implemented in AhsayOBM v8.3.4.0 to v8.3.6.x was found to cause issues on some VMware ESXi/vCenter v6, v6.5, v6.7, and v7 backup sets running in VDDK mode, related to both backup and restore. Ahsay has decided to temporarily revert to using VDDK 6 API until the VDDK 7 API bus has been addressed by VMware.
Until further notice, VDDK 6 API will be used for:
- All new installation of AhsayOBM v9.1.0.0 or above
- AhsayOBM upgrades from v6, v7 or pre-v9.1.0.0 to 9.1.0.0 or above
Affected existing AhsayOBM version with VDDK 7 API: AhsayOBM v8.3.4.0 to 8.3.6.x
Affected VMware versions: VMware ESXi/vCenter v6, v6.5, v6.7 and v7 backup sets running in VDDK backup mode.
To address the issues of clients with VMWare VDDK mode backup sets on affected AhsayOBM versions, it is strongly advised to immediately upgrade to AhsayOBM v9.1.0.0 or above. Once AhsayOBM is upgraded to v9.1.0.0 or above, the existing VMWare ESXi/vCenter v6, v6.5, v6.7, and v7 backup jobs will resume running without any further configuration or intervention needed.
Backup and Restore