pendrive clone impossible ?

[Anatoly]

On Sun, 1 Dec 2019 00:29:13 +0100
Tomasz CEDRO <tomek at cedro.info> wrote:

> but I have no more time to play, so I leave a trace if
> someone meets similar issues in future :-)

I've had a problem in the past with one of the first 32GB pendrives.
Not quite similar problem, but may it be buggy RAM cache
implementation too? What if:
- Write sector(s)
- usbconfig -d <your_bus>.<your_dev> power_off
- usbconfig -d <your_bus>.<your_dev> power_on
- Read and compare.

As you saying some writes was succeful, some not. May it
depend not on source of that bytes or their content, but on time passed
between write and read?

It turns out that Transcend pendrive I've got in 2010 had RAM cache
(didn't remember exact cache size I measured out, as I remember
something around 128K-512K), and all writes was cached. This amazingly
speeds up random R/W fs operations in comparation with similar
pendrives of those years, but I constantly losing the data and getting
fs corrupted when used it with OSes that do not "power_off" or
"suspend" that drive before I pull of it out of the socket.