Proxmox has officially unveiled the stable release of Proxmox Backup Server 4.0, marking a bold step forward in enterprise-grade backup solutions — now built on the latest technology stack with enhanced automation and scalability.

Beneath the Hood: Key Improvements in PBS 4.0

1. Debian 13 “Trixie” & Linux Kernel 6.14

• Built atop Debian 13 “Trixie”, delivering refreshed system libraries, enhanced performance, and improved security.
• Utilizes Linux kernel 6.14.8-2 as the new stable default, ensuring modern hardware compatibility and better throughput.

2. ZFS 2.3.3 with Live RAIDZ Expansion

• You can now add disks dynamically to existing RAIDZ pools without downtime, dramatically improving operational flexibility and eliminating extension-related service disruptions.

3. Native S3-Compatible Object Storage Support

• Technology-preview support for S3-compatible storage (e.g., AWS S3, MinIO, Wasabi) allows backups to public or private cloud storage.
• Local caching optimizes performance and minimizes costly API calls.

4. Smart Automation with Run-on-Mount Sync Jobs

• A new “run-on-mount” flag triggers synchronization jobs automatically as soon as removable datastores—like USB drives or NAS shares—are mounted.

5. Enhanced User Experience & GUI Improvements

• Cleaner consent flows, better handling of open ID consent windows, improved notification workflows, UI fixes, and strengthened security via HttpOnly cookies.

6. Flexible Network Handling

• Improved support for alternative interface naming in /etc/network/interfaces, helping maintain configuration stability even when kernel-driven interface names change.

Smooth Upgrade & Support Lifecycle

• Seamless in-place upgrade paths from PBS 3.x are available — just plan carefully, test backups, and follow documentation.
• PBS 3.4 will continue receiving security updates until August 2026, giving admins ample transition time.

Quick Overview Table

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