As per my previous issue with using SATA USB converters this issue happens sometime after a high data (70GB, 8hr) flow starts not always/ever at the same point in either data or time, it is inconsistent - sometime the enstire transfer works, other times not. The difference is that after the event the drive returns/reconnects as a valid accessible device whereas it did not before.
The USB SATA converter I'm using now is not AC powered, it 2 USB leads and I'm connecting it through a 4 port (powered) hub. The USB cable between the HUB and Pi has had the power lines cut so there is definitely no power back feed issue.
The 4 port hub also has a Ralink WiFi adapter in and it is wholly unaffected by any issues raised here.
To test this I just use the command
dd if=/dev/sda1 of=/dev/null
A success is where 70GB are read without issue, failures manifest as shown on the right.
I noticed that if there was some consistency about where I plug the USB cables and the issue.
Easy to blame the Hub, but the Ralink was unaffected.
I should point out that in doing these tests I was plugging and un plugging and not being consistent about which 2 of the HUB USB ports I used for Data/Power.
Doing the test again (consistently choosing the same port for each) I got these results from the dd before it died:
Swapping the connections around these are the figures (and I killed the DD, it was still running).
It would seem there is some sort of a fault on one port on my USB HUB. It's not dead, but the results definitely port toward a port that is the cause of the problem.
I've ordered a new USB HUB and until it arrives will simply not use that port for USB data!
I initially thought replacing the USB SATA converter/adapter had solved the inconsistent / unreliable USB HDD connectivity.
It didn't. The error had just changed.
The previous issue looked like this:
[ 1470.343321] usb 1-1.3: reset high-speed USB device number 4 using dwc_otg
[ 1470.423323] usb 1-1.3: device descriptor read/64, error -71
[ 1470.613336] usb 1-1.3: device descriptor read/64, error -71
It now looks like this:
51040.577529] usb 1-1.3.2: USB disconnect, device number 7
[51040.596515] sd 1:0:0:0: [sda] Unhandled error code
[51040.596547] sd 1:0:0:0: [sda] Result: hostbyte=0x01 driverbyte=0x00
[51040.596568] sd 1:0:0:0: [sda] CDB: cdb=0x28: 28 00 00 02 4e e0 00 00 f0 00
I still think their was an issue with the original adapter since the reset would always happen once during the 70GB / 8hr transfer, it was just never at the same point in either data or time. Now the transfer sometimes works.
Whilst I won't rule out a 5v rail power issue (on USB insert) there is definitely nothing wrong with the delivered power. The whole setup is powered by a 2.5A 5v device that doesn't drop below 4.95v.