PBS4.1 with DeuxFleurs Garage S3 backend storage - feedback and tweaks

dot.

New Member
Apr 21, 2026
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Hello dear Community,

I am running a PBS 4.1 server (community repo) which stores backups from a PVE 9.1 HA cluster (also community repo) to an on-prem DeuxFleurs Garage S3 storage cluster. The PBS has a local cache made of an RAID5 array which has a usable size of about 130GB.

I experienced a weird behaviour in that small-ish (50-70GB VMs) got backed up perfectly, but all backups of large (1TB+ VMs) eventually failed. This was consistent.

All physical hosts are on the same site, physically connected over a fast network that is definitely not a bottleneck of any kind.

What this forum thread is NOT:
  • A complain of any sort. S3 support is still labeled as "tech-preview" and shall be handled as such
  • A "pls-fix-asap" request to the dev team. Again, S3 support is tech preview
  • An attempt to get free support since I'm too cheap to buy commercial support (okay, my infrastructure is a private, home deployment, but anyway...)
I just wanted to share the workaround I implemented, it might help others...

So, there are 2 tweaks to implement:
  • On PBS, you need to enable the skip-if-none-match-header. From the CLI, enter:
proxmox-backup-manager s3 endpoint update garage-s3-ep --provider-quirks skip-if-none-match-header

  • On the Garage S3 gateway node (which accepts the client requests), you have to modify its nginx config file (/etc/nginx/sites-available/my_s3_example.conf) to change its buffering proxy to a streaming proxy behaviour by modifying the following section:
Code:
location / {
    proxy_pass http://my_S3_gateway_node;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Host $http_host;
    proxy_max_temp_file_size 0;
    proxy_connect_timeout 600s;
    proxy_send_timeout 3600s;
    proxy_read_timeout 3600s;
    proxy_http_version 1.1;
    proxy_request_buffering off;
}


After this, don't forget to restart the services (or reboot if you're unsure) and the backups to S3 will work like a charm!

Enjoy!

Denis