The technology of backing up virtual machines is described in Acronis Backup & Recovery 11.5 and Acronis vmProtect: Backup Algorithm on ESX Environment article.
The recovery operation can be performed either to the virtual machine (original or a new one) or using the File Recovery feature to restore only files and folders from a virtual machine backup.
Recovering to the virtual machine:
There are two ways for recovering virtual machines: to the original VM and to a new one. When recovery is performed to the original location, Acronis Backup for VMware (Acronis vmProtect) tries to locate the source VM using its InstanceUUID and if the VM is missed then the new VM will be created.
Recovering to original VM
In case original VM exists, the software uses the following algorithm:
- When the recovery operation is started Acronis software powers off and creates a quiescied snapshot of the target VM using VMware API. This technical snapshot is required to be able to rollback in case the recovery operation fails.
- After the snapshot is created Acronis software mounts virtual disks to the Virtual Appliance and recovers data to the existing disks. If Acronis Windows Agent is used or the Hot-Add functionality is not available, recovery is performed via network directly to the target VM.
- After data is recovered software disconnects virtual disks from the Virtual Appliance and sends command to remove the technical snapshot created in the first step.
- And only after all these steps are performed the target VM is started.
In this situation if the restore operation fails then the software will rollback using to the snapshot created in the first step.
Recovering to a new VM
If the original VM is missing or the option to recover to a new VM is chosen, the following algorithm is used:
- Acronis software sends command to create a virtual machine on the VMware ESXi host where the recovery is performed
- After the VM is created Acronis software mounts the freshly created virtual disks to the Virtual Appliance and recovers data to the existing disks. If Acronis Windows Agent is used or the Hot-Add functionality is not available, recovery is performed via network directly to the target VM.
- After the recovery is finished, the disks are disconnected and the VM is started.
The difference between these algorithms is that the snapshot creation is not required in case if new VM is created. Besides that if the recovery is performed to existing VM then the vmFlashBack feature can be used during recovery.
Recovering files using File Recovery option
The File Recovery option uses the following algorithm to restore data:
- Software exctracts chosen files/folders from the selected backup slice;
- A .zip archive is created with the content selected for restore.
- Download of the .zip archive via HTTP starts immediately. Processes of creating the .zip archive and downloading it to the client machine run simultaneously.