The Virtual appliance mode is not so efficient as the Direct storage access mode but provides better performance than the Network mode. The Virtual appliance mode is recommended if the role of a backup proxy is assigned to a VM.
In the Virtual appliance mode, Veeam Backup & Replication uses the VMware SCSI HotAdd capability that allows attaching devices to a VM while the VM is running. During backup, replication or restore disks of the processed VM are attached to the backup proxy. VM data is retrieved or written directly from/to the datastore, instead of going through the network.
The Virtual appliance transport mode can be used for all operations where the backup proxy is engaged:
- VM copy
- Quick migration
- Entire VM restore
- VM disk restore
- Replica failback
Requirements for the Virtual Appliance mode
To use the Virtual appliance transport mode, make sure that the following requirements are met:
- The role of a backup proxy must be assigned to a VM.
- The backup proxy and processed VMs must reside in the same datacenter.
- The ESXi host on which the backup proxy is deployed must have access to the datastore hosting disks of VMs that you plan to process.
- If you plan to process VMs that store disks on the NFS datastore, you must deploy the backup proxy on the same ESXi host where these VMs reside.
- The backup server and backup proxy must have the latest version of VMware Tools installed.
- SCSI 0:X controller must be present on a backup proxy. In the opposite case, VM data processing in the Virtual appliance transport mode will fail.
- The volume automount feature must be disabled. For details, see this Veeam KB article.
Limitations for the Virtual Appliance mode
- If a backup proxy used to process a source VM resides on a VMFS 3 datastore, it must be formatted with proper block size to be able to mount the largest virtual disk of hot-added VMs:
- 1 MB block size — 256 GB maximum file size
- 2 MB block size — 512 GB maximum file size
- 4 MB block size — 1024 GB maximum file size
- 8 MB block size — 2048 GB maximum file size
This limitation does not apply to VMFS-5 volumes that always have 1 MB file block size.
- For vSphere 5.1 the maximum supported VMDK size is 1.98 TB. For vSphere 5.5 and later the maximum supported VMDK size is 62 TB.
- Backup and restore of IDE disks in the Virtual appliance mode is not supported.
- Backup and restore of SATA disks in the Virtual appliance mode is supported if you use VMware vSphere 6.0 and later.