On August 5th, 2025, Proxmox rolled out the highly anticipated Proxmox VE 9.0 - ushering in a host of innovations for data center admins and homelab enthusiasts alike. Building on Debian 13 “Trixie” and packed with fresh features, this major release focuses on seamless upgrades, improved storage and networking, and an even more refined management experience. Here's an in-depth look at what's new and why you might want to consider upgrading.

Seamless Upgrade Experience

If you're running Proxmox VE 8.4, the move to version 9 is more straightforward than ever, with detailed guides ensuring an as-painless-as-possible migration path. For most deployments, the upgrade should require minimal service interruption, thanks to robust checklists and migration tools.

VM Snapshots Get a Power-Up

A standout feature in Proxmox VE 9.0 is technology preview support for VM snapshots on thick-provisioned LVM storages, introducing snapshots as volume chains. This enables persistent volume states and live snapshots on shared LVM storages - ideal for setups using iSCSI or Fibre Channel LUNs. A similar feature also arrives for Directory/NFS/CIFS storages, leveraging new qcow2 file handling for improved performance and reduced downtime during snapshot deletion.

High-Availability: Affinity Rules for Fine-Grained Control

High-Availability (HA) clusters are further refined with new node and resource affinity rules. You can now pin HA resources to specific nodes or require that certain resources always run together or apart - giving operators more powerful orchestration tools and replacing deprecated HA groups for a more modern and manageable HA configuration.

Fabrics: Next-Gen Software Defined Networking (SDN)

Perhaps the most significant SDN advancement is the introduction of Fabrics. These routed networks (now supporting OpenFabric and OSPF) allow for the creation of mesh topologies between nodes, enabling underlay networks for full-mesh Ceph clusters and streamlined VPN infrastructure. Fabrics automatically adapt to topology changes, modernizing both security and scalability of your Proxmox network stack.

Modernized Mobile Web UI

For those managing clusters on the go, the mobile interface is now completely overhauled. Rebuilt using Rust and the Yew framework, it offers a faster, more intuitive mobile experience - including quick overviews of guests, tasks, storages, and basic maintenance tools like VM start/stop directly from your phone or tablet1.

Storage and Backup Improvements

  • ZFS 2.3.3: Now supports adding disks to RAIDZ pools without downtime.
  • Dedicated Replication Network: Replication traffic can now travel via a dedicated network instead of sharing the migration line.
  • Proxmox Backup Server Compatibility: Enhanced performance for restores from Proxmox Backup Server-fetching data in parallel for faster recovery times.

Enhanced Metrics & Observability

Both node and guest monitoring get a boost: cgroup memory usage, CPU, and IO stall metrics are now available. Reporting granularity has been improved - metrics can be analyzed by minute, half-hour, six hours, or week. There's even an OpenTelemetry plugin for forwarding these metrics to your observability stack.

Network Management Gets Smarter

Frequent headaches with changing network interface names are eased with tools for interface pinning and expanded “alternative names” support - making network management less error-prone, even after upgrades or hardware swaps. You can use these names in both the OS networking and firewall rules for greater flexibility.

Improved Access Control & Security

  • Fine-Grained API Privileges: More control over QEMU guest agent commands for improved security.
  • Updated Privilege Model: The legacy VM.Monitor privilege is replaced with more granular rules, and a new VM.Replicate permission governs replication job access.
  • AppArmor 4.1: Enhanced kernel security, though admins should watch for regressions in third-party packages.

Known Issues & Breaking Changes

  • Support for GlusterFS storage is dropped.
  • Potential for network interface name changes after upgrade - monitor and adjust accordingly.
  • The maxfiles setting for backups is now fully deprecated.
  • Adjustments needed for custom roles referencing dropped privileges.

Conclusion

Proxmox VE 9.0 continues the tradition of open-source innovation with meaningful improvements in storage, networking, high availability, and usability. Its overhaul of SDN with Fabrics and the modernized mobile experience set a new standard for virtualization management. With robust upgrade pathways and granular control, it's a compelling release for established Proxmox operators and new users alike.