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This section provides a step-by-step description of a full virtual machine restore process implemented in Veeam Backup & Replication.
In the initialization phase, Veeam Backup & Replication prepares the resources necessary for full VM recovery. It performs the following steps:
- 1.Starts the necessary processes on the Veeam backup server.
- 2.Checks available backup infrastructure resources and assigns a proxy server for transferring restored VM data to the target host/datastore.
- 3.Communicates with Transport Services on the backup proxy and backup repository where the backup files reside. Transport Services, in their turn, start Veeam Data Movers. Veeam Data Movers on the backup proxy and repository establish a connection with each other for data transfer.
- 4.Connects to the vCenter Server or ESXi host where the restored VM will be registered.
Veeam Backup & Replication retrieves VM configuration data from the backup and restores it on the chosen ESXi host/datastore. Next, it instructs VMware vSphere to register the restored VM on the host. If a user selects to change VM configuration (for example, disk format or network settings) during restore, Veeam makes the necessary amendments.
Veeam Backup & Replication requests the vCenter Server or ESXi host to initiate a VM snapshot creation on the restored VM.
Important! A snapshot is not taken if a VM is restored to a VVOL datastore due to vSphere VDDK limitations (see https://pubs.vmware.com/Release_Notes/en/developer/vddk/65/vsphere-vddk-650b-release-notes.html).
Veeam Backup Manager instructs VMware vSphere to create virtual disks for the VM.
To write VM disk data to the target datastore, Veeam Backup & Replication can use one of the 3 transport modes:
- Direct SAN Access
- Virtual Applicance (HotAdd)
- Network (NBD)
This mode is available only for VMs that have all disks in thick provisioning.
In the Direct SAN Access mode, Veeam Backup & Replication connects to the ESXi host where the restored VM is registered. The ESXi host locates the VM disks, retrieves metadata about the disk layout on the storage, and sends this metadata to the backup proxy. The backup proxy uses this metadata to copy VM data blocks to the datastore via SAN.
In the Virtual Appliance transport mode, VM disks from the backup are hot-added to a virtualized Veeam backup proxy. The proxy connects to the ESXi host where the restored VM resides and transfers disk data to the target datastore through the ESX(i) I/O stack. When the data transfer process is finished, disks are unmapped from the backup proxy.
In the Network transport mode, Veeam backup proxy connects to the ESXi host where the restored VM resides, and writes VM disk data to the target datastore through the LAN channel.
After the proxy finishes writing VM disk data, Veeam Backup & Replication requests the vCenter Server or ESXi host to initiate a snapshot commit for the restored VM.