Proxmox Backup Server 3.4: Faster Cleanup and Smarter Offsite Sync

A backup you have never restored is a rumour, not a backup. Proxmox Backup Server 3.4, released in April 2025, does not change that fundamental truth, but it does remove two of the operational frictions that quietly discourage teams from running good backup hygiene: slow garbage collection and coarse sync filters.

What changed in 3.4

The headline improvements are speed and control. Garbage collection — the process that reclaims space from expired chunks — runs noticeably faster, which matters because a slow GC job is the most common reason teams extend retention beyond what they intended. Sync filters are now finer-grained, so you can be selective about which namespaces and groups replicate to an offsite target instead of shipping the entire datastore.

Deduplication changes the economics

PBS stores data in chunks and deduplicates aggressively, so the second and third full backups cost a fraction of the first. That changes what is practical: you can keep far more restore points online, and short retention becomes a choice rather than a necessity. Faster garbage collection keeps that economy honest, because it removes the temptation to skip cleanup.

Encrypt, but guard the key

Encryption at rest is straightforward in PBS, but the master key is the weak point. Losing it means losing every backup it protects. Store keys in a separate, documented location, and rehearse a key-rotation and recovery scenario before you depend on it. No sync-filter improvement will save you from a lost key.

Verification is the feature that matters

PBS can periodically verify backup integrity and detect bitrot before you ever need a restore. Enable verification jobs on a schedule and read the reports — a green checkmark you never look at is no better than no check at all. Offsite sync is only as good as the verification that runs against the remote copy too.

Build the routine

A trustworthy strategy is boring: scheduled backups, automated verification, regular restore drills, and an offsite copy you have actually tested. In our Backup Server workshop, the afternoon is dedicated to restores — full VMs, containers and single files recovered from a deliberately damaged datastore.

Trust is earned in rehearsals, not in promises. Schedule your next restore drill today.