Proxmox Backup Server (PBS) 4.0 Blog Series

Hot off the press is Proxmox Backup Server 4.0. PBS is a great tool to use with your Proxmox VE servers to do fast and easy backups of your VMs and LXCs. It’s very easy to setup, and can be deployed in a variety of forms: bare metal, VM or LXC.

Personally, I’ve deployed Proxmox Backup Server 4.0 as a VM on my primary Synology NAS. This PBS instance covers both of my Proxmox hosts, so I can back up all VMs and LXCs to one central server not hosted on any Proxmox VE servers.

The VM deployment is also the most flexible in terms of supporting a local virtual disk, iSCSI LUNs, NFS and S3 datastores. My PBS server uses VM-provisioned virtual disk for local storage, and an iSCSI LUN off a secondary local Synology NAS as a secondary datastore.

Core Platform Updates

Debian 13 “Trixie” Foundation

Updated to Debian 13 “Trixie” with Linux kernel 6.14
Includes ZFS 2.3.3 for improved storage capabilities
Enhanced hardware compatibility and security improvements

Major New Features

S3-Compatible Object Storage Support (Tech Preview)

Native support for S3-compatible object storage as backend for backups
Maintains a local cache to reduce repeated API calls and improve read performance
Requires 64-128 GiB local cache for optimal performance
Works with various S3 providers (AWS, Backblaze, Wasabi, etc.)

Live RAIDZ Expansion

ZFS 2.3.3 now allows to expand existing RAIDZ pools with minimal downtime
Users can now add new disks to an existing RAIDZ pool without downtime
Addresses a longstanding ZFS limitation

Automatic Sync Jobs for Removable Datastores

Users can now configure sync jobs to run automatically each time a relevant removable datastore is mounted
New “run-on-mount” flag on sync jobs
Simplifies datastore synchronization, especially in labs, field work, or air-gapped setups

Additional Improvements

Web Interface Enhancements

Fixes for datastore creation tasks not displaying properly
General UI polish and quality of life improvements

Integration and Compatibility

Proxmox Backup Server seamlessly integrates into Proxmox Virtual Environment
Supported upgrade path from Proxmox Backup Server 3.x to 4.0
Upgrade helper tool pbs3to4 available

Proxmox Backup Server 4.0 Blog Series

I’ve written a number of posts on PBS 4.0 to support various deployment scenarios. If you want to run PBS as a VM, check out these posts:

Depending on what type of datastore you want to use for backup storage, check out these posts:

If you are interested in more details about my iSCSI LUN mounting scripts, check out my Github repo:

iSCSI LUN Mounting Scripts for Proxmox Backup Server

If you prefer to run PBS as a lightweight LXC on one of your Proxmox VE hosts, I recommend using the Community Scripts: Proxmox Backup Server (LXC). At the time of this publication the script hasn’t been updated for PBS 4.0, but it should be in the coming weeks. You can then follow my first VM blog post above for detailed configuration steps.

Note: If you have a NAS and your PBS server is not running as a VM on your NAS, I suggest using an iSCSI LUN for your PBS datastore and not a NFS/CIFS mount. NFS mounts can be finicky and are not the preferred way to store PBS data.

Proxmox Backup Server 3.x to 4.0 Upgrades

If you are currently running Proxmox Backup Server 3.x and want to upgrade to 4.0, check out their official upgrade guide:

Upgrade from v3 to v4 – Proxmox Backup Server

I ran through the procedure without issue and it was pretty quick. Just make sure your PBS 3.x server is freshly updated to be at least 3.4.2-1 or later.

Summary

Proxmox Backup Server 4.0 is an incremental update for most home users over the prior 3.x version. The neatest new feature is supporting S3 object storage targets. This feature is only in tech preview, and I’ve seen some issues. So it’s great to experiment with, but not ready for prime time.