I installed volumio on Rpi 4. My music files are stored on an external USB SSD.
At startup the SSD is recognized and the music files are available in the library. After a few minutes, a popup message indicates that the “SSD is disconnected” and the files are no longer displayed in the library. In SSH, the SSD is still mounted and accessible, and the files are still present. Disconnecting and reconnecting the disk does not solve the problem. The only way is to restart volumio, but after a few minutes the disk disappears again.
However, if the SSD is powered by an external power supply, everything works fine.
You rPi is not an USB hub. Your SSD is extracting more current then the rPi can deliver. The USB Voltage will drop below 4.8V and the disk is going to be disconnected, in order to protect your rPi.
This is designed this way by Raspberry.
You jumping to your conclusion to fast, blaming it on a Volumio bug.
Keep the SSD external powered, or replace the SSD with a low current one. MAX 800mA peak current.
I’m a bit surprised: I have another Rpi on which the OS (raspbian) is directly installed on a USB SSD (the same Kingston A400 model). And in this configuration, the SSD always seems to be powered correctly because the system is stable.
Power consumption of the Kingston A400 :
0.642W (MAX) read / 1.535W (MAX) write
Under the 5V supplied by the USB port, this gives a current of 128mA max read and 307mA max write.
EDIT : According to some research, the Kingston A400 is recommended for use with the Rpi, as it consumes very little power.
Could it be the USB 3.0 → Sata adapter?