On Fri, 22 Jun 2012 02:30:54 +0100, "Arfa Daily"
put finger to keyboard and composed:

My 16 GB USB flash drive has developed an odd problem. It appears to have
become 'write protected' all on its own. It doesn't have a switch anywhere
before everyone jumps on their keyboards ...

I have tried everything to mount the bloody thing and force a reformat, but
to no avail. Looking on the net, there are lots of references to the
problem, and even a little software utility that lots of posters have tried,
and had success with. I downloaded it and tried it, but nope - problem
persists.

I'm no guru, but ISTM that your flash drive may have reached the end
of its life. I think the failure mechanism may be something like the
following.

When data are written to a cell, the original contents first need to
be erased, they cannot just be overwritten. Since data are written in
whole blocks rather than individual LBAs (aka sectors), the original
block is copied to a new location and the pointers are then updated so
that the LBAs now map to the new block. The old block can then be
reused at a later date. That's how wear levelling works.

AIUI, USB flash drives and SSDs are "over-provisioned" with additional
storage space to accommodate spare sectors, etc. It could be that your
flash drive has now exhausted its over-provisioned space, in which
case there are no spare sectors to receive your new data. That could
be why the drive is reporting that it is "write protected".

Note that "erasing" files or formatting the drive still requires that
the original data be copied to a new location. SSDs can be erased
using the ATA Secure Erase command, but AIUI there is no similar
command for USB mass storage devices. The latter use a SCSI-like
command set. The Secure Erase command is performed internally by an
SSD or HDD -- it does not require the OS to write zeros to every
sector over the SATA/PATA interface.

BTW, which "little software utility" have you tried?

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.