I have configured miniDLNA, SMB, and Plex on a Linux system with an external HDD. If the Plex Media Service is disabled, the disk goes into sleep mode without any issues (it is not running at all, and there is no noise). However, when the Plex Media Service is enabled, the disk is always active — even though there is no active playback from any clients.
You can go into your library settings, you can minimize, but not prevent Plex from accessing its database or log files periodically.
Folks have complained about this since the very beginning.
It’s how Plex works.
You’re actually doing more harm (wear & tear) on the HDD by spinning it down & up all the time. It will last a lot longer if the heads remain loaded over the platters and the drive at a stable operating temperature
Actually, HDD goes to sleep mode now. It was just scanning some files earlier. However, I decided to disable “Generate video preview thumbnails,” “Generate chapter thumbnails,” “Analyze audio tracks for loudness,” and “Perform extensive media analysis during maintenance.”
Also, I initially thought I had to disable “Scan my library automatically (Your library will be updated automatically when changes to library folders are detected.)” to allow the HDD to become inactive. However, it turns out that’s not necessary, and the HDD can still enter sleep mode. This option is very important anyway, so everything works fine now. It of course can wake up from time to time, but rarely
