Replication Components

The following infrastructure components are engaged in the replication process:

• Backup server
• Source host and target host with associated datastores
• One or two backup proxies
• Backup repository
• [Optional] WAN accelerators

Backup Server

The backup server is the configuration, administration and management core of the replication infrastructure. During the replication process, the backup server coordinates replication tasks, controls resource allocation and replica job scheduling.

Source and Target Hosts

The source host and the target host produce two terminal points between which replicated VM data is moved. The role of a target can be assigned to a single ESX(i) host or to an ESX(i) cluster. Assigning a cluster as a target ensures uninterrupted replication in case one of the cluster hosts fails.

Backup Proxies

To collect, transform and transport VM data during the VM replication process, Veeam Backup & Replication uses Veeam Data Mover Services. Data Mover Services communicate with each other and maintain a stable connection.

For every replication job, Veeam Backup & Replication requires three Data Mover Services:

• Source-side Data Mover Service hosted on the backup proxy
• Target-side Data Mover Service hosted on the backup proxy
• Data Mover Service hosted on the backup repository

During replication, the source-side Data Mover Service interacts with the source host and the target-side Data Mover Service interacts with the target host. The Data Mover Service hosted on the backup repository works with replica metadata files.

To streamline the replication process, you can deploy a backup proxy on a VM. The virtual backup proxy must be registered on an ESX(i) host that has a direct connection to the target datastore. In this case, the backup proxy will be able to use the Virtual appliance transport mode for writing replica data to target. For more information, see Transport Modes.

During the first run of a replication job, Veeam Backup & Replication creates a replica with empty virtual disks on the target datastore. If the Virtual appliance mode can be used, replica virtual disks are mounted to the backup proxy and populated through the ESX host I/O stack. This results in increased writing speed and fail-safe replication to ESX targets.

If the backup proxy is deployed on a physical server or the Virtual appliance mode cannot be used for other reasons, Veeam Backup & Replication uses the Network transport mode to populate replica disk files.

Backup Repository

The backup repository stores replica metadata. The backup repository must be deployed in the source site, as close to the source host as possible. When you perform incremental replication, the source-side Data Mover Service communicates with the Data Mover Service on the backup repository to obtain replica metadata and quickly detect changed blocks of data between two replica states.

WAN Accelerators

WAN accelerators are optional components in the replication infrastructure. You can use WAN accelerators if you replicate VMs over a slow connection or over WAN.

In the replication process, WAN accelerators are responsible for global data caching and deduplication. To use WAN acceleration, you must deploy two WAN accelerators in the following manner:

• The source WAN accelerator must be deployed in the source side, close to the backup proxy running the source-side Data Mover Service.
• The target WAN accelerator must be deployed in the target side, close to the backup proxy running the target-side Data Mover Service.