According to the Veeam Backup & Replication Best Practice Guide1, the proxy and repository servers are the components that should be sized correctly to ensure that synthetic operations and backup copy jobs can be completed in the desired window. This is because:
*The proxy server is responsible for retrieving data from the source and sending it to the target. The proxy server performance depends on the CPU, memory, network, and storage resources available. The proxy server should have enough CPU cores and memory to handle concurrent tasks, as well as sufficient network bandwidth and storage throughput to transfer data efficiently.
*The repository server is responsible for storing backup files on the target storage. The repository server performance depends on the CPU, memory, network, and storage resources available. The repository server should have enough CPU cores and memory to handle concurrent tasks, as well as sufficient network bandwidth and storage throughput to write data efficiently. The repository server should also support the backup format and retention policy chosen for the backup copy job.
References: 1: Backup copy jobs - Veeam Backup & Replication Best Practice Guide