druck  wrote:
> On 01/01/2021 20:53, bob prohaska wrote:
>> Just tried using a couple of USB card adapters with my 8GB Pi4.
>> Both cause immediate loss of USB hard disk access. Unplugging
>> the offending adapter does not restore normal operation. Power
>> cycling puts matters right without apparent ill effect.
>
> Do you have your USB hard disk mounted using the device name (/dev/sdaX)
> or a disk UUID (UUID=blahblahblahblah) ?
>
It's the default setup, using UUID. The machine was already running,
so that shouldn't matter. Plugging in the adapter seemed to cause
a persistent USB error, it was the persistence that seemed most odd.
There's no powered hub involved, on the thesis that a 3.5 amp power
supply and a USB 3.0 port should be ok on their own. Indeed, the
machine boots hands-off from the mechanical hard disk.

I did do a power supply check. It's not quite as good as expected,
5.08 volts booted and idle, 5.00 to 5.03 volts between GPIO pins
2 and 39 while running the "SD card speed test" which appears to
be a "boot device speed test" instead. That seems good enough to
support a USB-microSD  adapter being plugged in. Of course, a DVM
is blind to transients, so it's of limited use.

I'll wait until I don't mind crashing the machine and try again
using the USB 2.0 ports.

Thanks for writing,

bob prohaska


>
> ---druck

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