README: BBR for backups over a long distance

2026-10-18 01:26:27 +02:00
parent 01e16199f7
commit 5af712acc3
2 changed files with 10 additions and 0 deletions
@@ -175,6 +175,13 @@ Contributions welcome via PR — add what you ran into with your own provider.
  the backend being listed is not proof it will work here. Once the extension is present it works
  the same as any other backend; no ng_backup-specific config beyond host/share/user/password.

+- **Backups over a long distance (high latency):** on Linux, the default TCP congestion control
+  (cubic) slows a single connection down a lot on a long line with some packet loss. From Canada to
+  an S3 bucket in Warsaw (114 ms), one upload went from 2.4 to 7.5 MiB/s after switching the
+  server (or the VM/container host where TCP ends) to BBR:
+  `sysctl -w net.core.default_qdisc=fq net.ipv4.tcp_congestion_control=bbr`
+  (`modprobe tcp_bbr` first; make it permanent in `/etc/sysctl.d/`).
+
 - **NFS is not a files_external backend at all.** Mount the NFS export on the server yourself
  (e.g. via `/etc/fstab` or a systemd `.mount` unit) and point ng_backup's `local` backend at the
  mount point; ng_backup never mounts or unmounts anything on its own, so an NFS mount dropping