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Veeam Backup & Replication Help Center  > Best Practices >  Resource Planning > Proxy Server and Transport Modes > Data Transport Modes for Backup Proxies > Network Mode (NBD)

Network Mode (NBD)

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Network mode is by far the easiest backup mode to implement, as it requires no additional configuration. Veeam always uses this mode at least to back up and restore VMware configuration files and to read Change Block Tracking information.

When in this mode, the backup proxy will connect to ESXi hosts on VMkernel interfaces by DNS name resolution and use this connection to transport data, utilizing Veeam’s file copy technology (also known as FastSCP). Remember that the backup proxy requires several ports to be open, as described in the User Guide: https://helpcenter.veeam.com/backup/80/vsphere/used_ports.html.

noteNote

It is highly recommended to maintain a good network connection between the VMware ESXi VMKernel port and Veeam Backup & Replication, as it will be used by many other features like Instant VM Recovery, Virtual Lab and SureBackup, Linux FLR appliance, etc.

For load balancing, Veeam uses a selection of proxy servers based on the network subnet:

Backup proxies in the same subnets as the VMKernel interfaces (DNS Name of ESXi hosts) are selected if you have the Automatic Selection proxy setting configured in the backup jobs.

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If proxy servers do not run in same subnets as the VMKernel interfaces of the ESXi hosts, you will have to manually select the proxies that will process your backup jobs, otherwise it is possible that proxies from other sites will be used to transport data.
You can select all proxies from the same site to enable load balancing in that case.

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In case you work with several branches or datacenter environments, it is also recommended that you manually choose the proxies (per site) in the job settings - to streamline and speed up the load balancing.

Pros

Network mode can be used for both backup and restore.

Can work with both physical and virtual backup proxies.

Being the most mature of all transport modes, it supports all types of storages.

Is recommended for use in virtual deployments with NFS-based storage systems, as it helps to minimize VM stunning. See also the “Considerations for NFS Datastores“ section of this guide.

Performance on 10 Gb Ethernet is highly positive.

As data transfers initiate very quickly, the Network mode is preferable for processing incremental backups on relatively static servers (that is, VMs with small amount of changes).

Can be helpful when you have plenty of clusters with individual storage configurations (e.g., at hosting providers). In such deployments, using the Network mode for data transfer can help to reduce Veeam footprint and costs, as well as to increase the security (if compared to other modes and storage configuration).

Cons

Typically, Network mode uses only 40% of the physical available bandwidth of the external VMKernel Interface connection due to throttling mechanisms implemented on the management interfaces of VMware vSphere 4.x-5.x.

Is rather slow on 1 Gb Ethernet (about 10-20 MB/s) also due to throttling mechanisms, so restores via the Network mode will take quite a long time.

adviceTip

You can influence the usage of the specific VMKernel interface by modifying the DNS name resolution for all Veeam backup servers (for example, by adding entries in the hosts file or by using special DNS configuration).

Recommendations

As the Network mode is relatively inefficient in bandwidth usage, consider setting up at least one virtual backup proxy for hot-add restores – then it will be possible to achieve higher throughput and thus lower RTO.

You can also restore to a thin disk format and later use standard VMware methods to change the disk format to thick disk, if needed.

Another way to overcome this limitation is to use Instant VM Recovery with Storage vMotion (if licensed on the VMware vSphere side).

As there is no overhead (like SCSI disk Hot-Add, or search for the right volumes in Direct SAN) on backup proxies, the Network mode can be recommended for scenarios with high-frequency backups or replication jobs, as well for environments with very low overall data and change rate (VDI).

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