I’d forgotten how convoluted USB protocol and power regulation can be, and how the Raspberry Pi doesn’t usually help matters. After I powered the Raspberry Pi up, with the external SSD plugged in, for the first time, I ran sudo fdisk -l command via SSH. It showed a list of the SD card drives (root and boot), but got stuck when trying to read the SSD. I couldn’t even ctrl+C out of the operation.
I first jumped to the conclusion that the external SSD was drawing too much power at about 900mA. That seems like a lot, but USB hubs with separate power supplies, that could potentially serve as an external SSD PSU are also expensive, and can be flaky when handling the client/host power draw negotiations. Apparently the USB ports can easily supply 1A of power. The cutoff seems to be 1.5A, with 1.2A the nominal running max. So my measly 0.9A drive is probably not the cause. My USB C charger is 3A, the cooling fan consumes 0.3A, at the very most, and the Pi itself can draw up to about 0.9A when doing something terribly fancy (see chart above). So my worst case scenario power consumption should be far below the USB port limit and the Power Supply limit, which is 3.0A:
Raspberry Pi ......... 900mA
Cooling fan .......... 300mA
External SSD ......... 900mA
-----------------------------
Total Consumption .... 2100mAOut of desperation I booted the SSD on my laptop and changed the drive from NTFS to ext4. This time the Pi had no trouble running the fdisk command. That surprised me, but I guess the pi really needs some tlc for NTFS to work properly. Check out raspberrypi.org for more on that subject:
Raspberry Pi External storage configuration
While reading about the various issues that the Pi 4 has with UAS devices, I came across several posts complaining about issues they were having running SD600Q USB 3.2 External Solid State Drives with their Raspberry Pi 4’s… I guess I probably should have done some research before rushing out and buying it, but I mean, what are the chances???
keep documenting 