What Is Proxmox Backup Server? A Complete Overview of PBS

Beyond Basic Backups

Proxmox Backup Server (PBS) is a dedicated, enterprise-grade backup solution designed specifically for Proxmox VE environments. While Proxmox VE includes built-in backup capabilities through vzdump, PBS takes backup and recovery to a different level with features like block-level deduplication, incremental-forever backup chains, client-side encryption, and efficient storage utilization. Like Proxmox VE, PBS is free and open-source under the AGPL v3 license.

How PBS Works

PBS operates as a separate server (physical or virtual) that receives backups from your Proxmox VE nodes. It uses a chunk-based storage architecture where backup data is split into fixed or variable-size chunks, each identified by its cryptographic hash. If the same chunk already exists in the datastore, it is not stored again. This deduplication happens at the block level, which is far more efficient than file-level deduplication.

# PBS architecture overview:
# PVE Node 1 ──┐
# PVE Node 2 ──┼──> Proxmox Backup Server ──> Datastore (deduplicated chunks)
# PVE Node 3 ──┘

Deduplication

Deduplication is the headline feature of PBS. When you back up 10 similar VMs running the same operating system, PBS stores the shared blocks only once. A second full backup of the same VM typically stores only the changed blocks. In practice, this means your backup storage can hold significantly more backups than the raw capacity would suggest. Deduplication ratios of 3:1 to 10:1 are common depending on workload similarity.

Incremental-Forever Backups

Traditional backup strategies require periodic full backups that consume time and storage. PBS uses an incremental-forever approach: the first backup is a full backup, and every subsequent backup transfers only changed data blocks. Despite this, every backup is a complete, independently restorable snapshot. There is no need to chain through multiple incremental backups during a restore.

# Typical backup job output showing incremental efficiency:
# Upload stream: 120.00 GiB in 847.23s (144.94 MiB/s)
# Uploaded new chunks: 2.31 GiB (1.93% of stream)
# Reused chunks: 117.69 GiB (98.07% of stream)
# Only 1.93% of data was new — the rest was deduplicated

Encryption at Rest

PBS supports client-side encryption where data is encrypted on the PVE node before being sent to the backup server. This means the PBS server never sees unencrypted data, which is essential for compliance requirements and multi-tenant environments. Encryption uses AES-256-GCM and the encryption key stays on the client side.

# Generate an encryption key
proxmox-backup-client key create /etc/pve/priv/encryption-key.json

# Create a paper key backup (print and store securely)
proxmox-backup-client key paperkey /etc/pve/priv/encryption-key.json

Critical: Store your encryption key securely. If you lose it, your encrypted backups are permanently unrecoverable.

Verify Jobs

Backups are only useful if they are actually restorable. PBS includes verify jobs that check the integrity of stored backup data. Verification reads all chunks referenced by a backup and validates their checksums. You can schedule verify jobs to run automatically and receive notifications if any corruption is detected.

# Verify a specific backup from the CLI
proxmox-backup-client verify --repository backup-server:datastore1

# Verify jobs can also be scheduled in the PBS web UI:
# Datastore > Verify Jobs > Add

Garbage Collection

As you prune old backups, the chunks they referenced may no longer be needed. Garbage collection (GC) identifies and removes orphaned chunks to reclaim disk space. GC runs in two phases: first marking all chunks that are still referenced by at least one backup, then removing unmarked chunks.

# Run garbage collection manually
proxmox-backup-manager garbage-collection start datastore1

# Check GC status
proxmox-backup-manager garbage-collection status datastore1

GC should run regularly — most administrators schedule it daily or weekly depending on backup frequency.

Integration with Proxmox VE

PBS integrates directly into Proxmox VE's storage model. You add your PBS server as a storage target in PVE, and it appears alongside your other storage backends. Backup jobs in PVE can target PBS just as easily as a local directory or NFS share.

# Add PBS storage to Proxmox VE via the CLI
pvesm add pbs pbs-backup \
  --server 192.168.1.50 \
  --datastore main-store \
  --username backup@pbs \
  --password yourpassword \
  --fingerprint XX:XX:XX...

Once configured, you schedule backup jobs through the PVE web UI as normal, selecting the PBS storage as the target.

When to Use PBS vs vzdump Alone

Proxmox VE's built-in vzdump tool can back up VMs and containers to local storage, NFS, or CIFS without PBS. For small environments with a few VMs, vzdump to an NFS share may be sufficient. However, PBS becomes valuable when:

• You have many VMs with similar content (deduplication saves significant space)
• You need to retain many backup generations without massive storage requirements
• Backup window is limited and only changed data should be transferred
• You require encryption for compliance or security reasons
• You need verified, integrity-checked backups with automated reporting
• You want a centralized backup target for multiple PVE nodes or clusters

For monitoring your backup infrastructure alongside your VMs, tools like ProxmoxR can help you keep an eye on backup task status from your mobile device, ensuring you catch any failures promptly.

Getting Started with PBS

PBS can be installed on bare metal or as a VM within your Proxmox VE cluster (ideally backed by storage that is independent from the production storage you are protecting). The installation follows the same process as PVE — download the ISO, flash it to USB, and run the installer. Within minutes, you have a dedicated backup server ready to protect your virtual infrastructure.