This is a Raspberry Pi 2 using a 5V 2 Amp power supply running with a LaCie 2TB USB external drive connected via the USB port. It gets its power from the USB port for the drive.
The above has been running successfully for many months without a problem until recently, when I did a fresh install of Jessie. In that process there may have been a firmware update too.
What happens now, if the USB external drive is connected to the Raspberry Pi 2 during boot up, it doesn't complete boot. If it is plugged in while the system is up and running normally, it creates a lot of information in the logs and the drive makes a "clicking" sound. It displays the message "over-current change" in the log.
I should mention the USB external hardware drive works without the assistance of a USB powered hub on a Mac and a Dell server.
For detail of the log and background see my other post: After upgrade to Jessie, crashes when external USB drive is connected
This is a reproducible problem now, and not sure what the cause of it is. Can I roll back to a previous firmware?
I have connected a USB powered hub to the Raspberry Pi 2, and the USB external drive to the USB hub and the system runs fine as before and no issues. Why after all these months, is there a power issue? Or is it something in the firmware?
With no other problems, could the power supply all the sudden be faulty like this?
I even rolled back the OS to Wheezy and it doesn't work with the USB drive directly connected to the Raspberry Pi 2 either. I need to use the USB powered hub.