Veeam Backup & Replication uses the following components for the replication process:
- Backup server
- Source host and target host with associated datastores
- One or two backup proxies hosting Veeam Data Movers
- Backup repository
- [Optional] WAN accelerators
All backup infrastructure components engaged in the job make up a data pipe. The source and target hosts produce two terminal points for the data flow. Veeam Backup & Replication processes VM data in multiple cycles, moving VM data over the data pipe block by block.
The backup server is the configuration, administration and management core of the backup infrastructure. During the replication process, the backup server coordinates replication tasks, controls resource allocation and replica job scheduling.
The source host and the target host produce two terminal points between which replicated VM data is moved. The role of a target host can be assigned to a single ESXi host or ESXi cluster. Assigning a cluster as a target ensures uninterrupted replication in case one of the cluster hosts fails.
To collect, transform and transport VM data during the VM replication process, Veeam Backup & Replication uses Veeam Data Movers. Veeam Data Movers communicate with each other and maintain a stable connection.
For every replication job, Veeam Backup & Replication requires three Veeam Data Movers:
- Source Veeam Data Mover hosted on the source backup proxy
- Target Veeam Data Mover hosted on the target backup proxy
- Veeam Data Mover hosted on the backup repository
During replication, the source Veeam Data Mover interacts with the source host and the target Veeam Data Mover interacts with the target host. The Veeam Data Mover 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 ESXi 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.
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 ESXi host I/O stack. This results in increased writing speed and fail-safe replication to ESXi targets. For more information, see Transport Modes.
If the backup proxy is deployed on a physical machine or the Virtual appliance mode cannot be used for other reasons, Veeam Backup & Replication uses the Network transport mode to populate replica disk files.
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 Veeam Data Mover communicates with the Veeam Data Mover Service on the backup repository to obtain replica metadata and quickly detect changed blocks of data between 2 replica states.
WAN accelerators are optional components in the backup 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 2 WAN accelerators in the following way:
- The source WAN accelerator must be deployed in the source side, close to the backup proxy running the source Veeam Data Mover.
- The target WAN accelerator must be deployed in the target side, close to the backup proxy running the target Veeam Data Mover.