Veeam Backup & Replication software differentiates between different classes (tiers) of storage where backup files are placed. A Scale-Out Backup Repository (SOBR) includes Performance tier, Capacity tier, and Archive tier. 

Block Sizes - A Pivotal Parameter

By default, Veeam Backup & Replication software writes smaller block sizes (64KB-1MB). Smaller block sizes are better suited for deduplication and more granular restores, especially important for the first stage in backups – on the performance tier.

When incorporating the secondary Capacity tier for longer retention backups, larger block sizes (e.g., 8 MB) are recommended. Swarm object storage performs well with larger block sizes, and the space occupied by backups can be reduced through Erasure Coding.

There is only one block size setting that affects both the performance and capacity tiers.