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In my first post in my Raspberry Pi NAS series, I mentioned I had issues with my external hard drives and had to buy an external (powered) USB hub, but I didn’t elaborate further.

What’s The Issue?

Among the many changes from its predecessor, the Raspberry Pi 4 now uses USB-C as its power supply rather than MicroUSB.

One downside of that? Maximum power draw of 1.2A…

What problems did that cause?

I kept seeing my 2x USB external HDDs being inaccessible and IO operations hung, requiring a reboot to restore service.

This was happening at least once per day, and I would see logs such as

[512.7159387] usb usb2-port: over-current change #1
[512.950593] usb 2-2: USB disconnect, device number 3
[512.952267] Buffer I/0 error on dev sdbl, logical block 1290, lost async page write

What did you do to resolve it?

I tried a number of things including tweaking power management settings using hdparm, installing stress to stress test the CPU and I/O and eventually settled on buying an externally powered USB hub.

While this did help a little, ultimately the fix was to uninstall smartmontools due to this issue.

As ever, thanks for reading and feel free to leave comments down below!