Hi everyone,

I’m trying to diagnose a strange Plex performance issue on my Unraid server and would appreciate any ideas. I apologise in advance if this is not the right place for this post I wasnt sure where it fits because the issue is still unclear to me

System:

• Unraid kernel: Linux 6.12.24-Unraid x86_64

• Motherboard: Supermicro X10DRi-T4+

• CPU: Dual Intel Xeon E5-2699 v4

• RAM: 128 GB DDR4 ECC

• GPU: Intel Arc A380

• Plex container appdata: 2 TB WD m.2 NVME cache drive, fs BTRFS

• Media storage: ~340 TB Unraid array

• Plex running in Docker on Unraid
  

The issue:

Plex browsing is extremely slow. Posters, metadata, home screen rows, and library sections take a long time to load. However, once I click play, playback is perfect. Direct play and transcoding both work without buffering.

So the problem is not playback performance. It seems specifically related to metadata/library loading.
Here is an example of what I mean
https://imgur.com/a/rREBqrn

What I tested:

1. Existing Plex Docker on Unraid (at first i had thought it was a database/plex config error) I've deleted plex appdata and started everything from scratch - made no difference

   • Slow browsing/loading metadata

2. Fresh Plex Docker install on Unraid, same libraries. Tried different repos as well - binhex, official (plexinc/pms-docker), lscr.io/linuxserver/plex

   • Same slow browsing issue
     

3. Plex Media Server installed on my Windows admin PC, accessing the same Unraid media over SMB. That fixed it. Browsing was instant when the server ran on my pc. At first I though it might be that my pc has better hardware for plex. but then..
   

4. Windows 10 VM running inside the same Unraid server, Plex installed inside the VM, accessing the same Unraid media over SMB Browsing/loading is also instant!! It seems like running it on windows fixed it regardless of the hardware
   here is an example of how the virtual machine performed
   https://imgur.com/a/Zo4ovBi
   

This is what confuses me most. Plex inside a Windows VM on the same Unraid machine performs instantly, but Plex Docker on Unraid is slow.

My suspicion (as a super noob):

I’m wondering if this is related to:

• Plex appdata being on BTRFS?

• BTRFS CoW/write amplification with Plex metadata/database/cache (This is what chatgpt suggested)

I’m considering moving Plex appdata to an XFS or EXT4 SSD pool, or disabling CoW on the Plex appdata directory and rewriting the files.

Questions:

Any advice on what to test next would be appreciated

Have you ever looked at the Plex log when you click on a movie? The Docker container is running as host as well, right? (not bridge right?)

I think most of us have the appdata on a BTRFS Pool and i don't think that will be a Problem.

Edited June 2Jun 2 by Elyeu