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

• Backups are first written on the Performance tier using local storage, DAS, NAS, and SANs to speed up backup and restoration.

• The Capacity tier on object storage is intended to provide more space for longer-term retention of backups at a lower cost. When backups reach a certain age, they are automatically migrated to the Capacity tier. Alternatively, the second copy of particularly important backups is kept there for extra redundancy. Swarm provides an ideal object storage platform for the Capacity tier.

• The Archive tier is currently reserved for rarely accessed cold backups on low-cost Amazon Glacier or Azure Archive Storage.

Block Sizes - A Pivotal Parameter

By default, Veeam Backup and 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.