Wi-Fi power saving was breaking my Immich uploads

TLDR

If your Linux machine slows down under heavy uploads over Wi-Fi, first check if power saving is enabled:

iw dev wlp6s0 get power_save

If you see:

Power save: on

then disable Wi-Fi power saving:

sudo nano /etc/NetworkManager/conf.d/wifi-powersave-off.conf

[connection]
wifi.powersave = 2

Restart NetworkManager. That fixed the issue for me.

Setup

I run Immich on an Ubuntu server connected over Wi-Fi. My phone backs up photos to it over the same local network.

Nothing fancy. No WAN access.

The Problem

Everything works fine until the bulk upload starts from the phone.

As soon as Immich begins syncing photos and videos:

Internet speed on the server drops from ~250 Mbps to below 1 Mbps
Ping jumps from ~6 ms to 60+ ms
Upload slows down or stalls
Even basic browsing on the server becomes painful

CPU, RAM, and disk were mostly idle.

One detail stood out:

Reconnecting Wi-Fi instantly fixed connection speed

But only until the next upload.

What Made This Confusing

This was all happening inside the same LAN.

So:

no internet bottleneck
no router overload
no obvious bandwidth limit

At first it looked like a random network issue, but the “reconnect fixes it” pattern pointed to something local.

The Actual Cause

I found this in NetworkManager config:

[connection]
wifi.powersave = 3

Default location:

/etc/NetworkManager/conf.d/default-wifi-powersave-on.conf

This enables Wi-Fi power saving.

Why This Breaks Uploads

Immich uploads use HTTP, so this is TCP traffic.

During a large upload:

the phone sends a continuous stream of data
the server must respond continuously (ACKs and control packets)

Wi-Fi is half-duplex, so sending and receiving compete with each other.

With power saving enabled:

the Wi-Fi interface delays transmissions
latency increases under sustained traffic
packet timing becomes inconsistent

TCP reacts to this as congestion and reduces throughput aggressively.

That is why everything slows down, not just the upload.

Fix

Create an override config:

sudo nano /etc/NetworkManager/conf.d/wifi-powersave-off.conf

Add:

[connection]
wifi.powersave = 2

Restart:

sudo systemctl restart NetworkManager

Verify:

iw dev wlp6s0 get power_save

Expected:

Power save: off

After this change:

uploads run at normal speed
latency stays stable
no more stalls
no need to reconnect Wi-Fi

Takeaway

My system uses a MediaTek MT7922 Wi-Fi chipset. It works fine in general in Linux kernel 6.10 or newer, but seems sensitive to power saving under load.

Linux enables Wi-Fi power saving by default because most systems are laptops. But if your machine behaves like a server, this default can hurt performance.

This was not an Immich issue or a network limitation. Just a default setting that did not match the use case.