How Cloud-PBS synchronizes Proxmox Backup Server with object storage

Cloud-PBS includes automatic synchronization between your Proxmox Backup Server instance and object storage. This article provides a technical overview of how this works.

Architecture overview

Cloud-PBS uses a two-tier storage architecture:

1. Primary tier: Your dedicated PBS instance with fast block storage, optimized for backup and restore operations
2. Secondary tier: Object storage for long-term redundancy and durability

The synchronization process runs continuously in the background, ensuring that your backup data is replicated to the secondary tier without any impact on your backup operations.

How synchronization works

Continuous replication

As new backup data arrives on your PBS instance, Cloud-PBS detects the changes and schedules replication to object storage. This process is:

• Asynchronous — does not impact backup performance
• Incremental — only changed data is replicated
• Verified — data integrity is checked after replication

Consistency guarantees

The synchronization process ensures that complete backup snapshots are replicated. Partial snapshots are never stored in object storage, so you can always restore a consistent state.

Retention alignment

Object storage copies follow the same retention policies as your primary PBS storage. When a snapshot expires on the primary tier, it is also removed from object storage.

Benefits

• 11 nines durability on the object storage tier
• Geographic separation between primary and secondary storage
• Automatic operation — no configuration required
• No additional cost — included in all Cloud-PBS plans

Encryption and synchronization

When client-side encryption is enabled, the synchronized data remains encrypted. Object storage stores the same encrypted chunks as the primary tier — we never decrypt your data during synchronization.

Start your Cloud-PBS trial to benefit from automatic storage synchronization.