4 GB USB flash disk with FAT ok, with ext3 corrupted files

Miernik public at miernik.name
Mon Jun 18 08:59:44 UTC 2007

Alan Stern <stern at rowland.harvard.edu> wrote:
> What you should do is fill up the drive with known data (not just 0's 
> like in your dd test), and then read it back to see if the data has
> changed.

Using dd I found out the reason of the problem:


These USB sticks are fake, and have a 1 GB flash chip, and a fake
controller which makes the computer think it is a 4 GB stick.

Any data written past the first 1066401792 bytes is lost, and reading
any data over that boundary gives a copy of the last 2048 bytes of the
real flash chip, repeated as many times to fill the whole stick.

I taken one of the sticks apart. The flash chip is

The controller is


Sorry for wasting your time. But the benefit is that now searching for
the error messages that I encountered in Gmane or Google will reveal
this thread with the real cause.

It's only very strange that if 95% of the sticks sold on eBay are such
fake's, then why noone on this mailing list about USB knew about and my
Googling for the error messages didn't reveal any posts about the cause.
I hope this post will fix this lack of knowledge spread.

I am also very surprised that these sellers manage to get positive
comments for these sticks, and the people who buy them don't notice?
People don't fill them past 1 GB? If so, why buy a 4 GB stick, you could
have bought a 1 GB one? And when they fail a lot of time after they buy
it, when they finally try to fill it past 1 GB and actually read that
data, maybe its so lot of time since they bought it by average that they
think that the stick just got broken? Am I one of the few ones who tried
to fill it past 1 GB on the first day I got it?


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