"Franc Zabkar" wrote in message
...
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.


Thanks for that explanation. I guess it's a possibility. The utility I tried
is called "Repair_v2.9.1.1.exe'

I downloaded it from a website after Googling on "Flash drive says it is
write protected". Many of the hits that returned made reference to this
utility, and provided a link to the URL where it is to be found. Almost
everybody reported total success from using it, but there were a few cases
like mine, where it didn't work.

I guess I'm just going to have to buy a new one. They are not expensive.
It's just annoying to be beaten by something as simple as a corrupted file
structure. It has been suggested to me that there are Linux ways of forcing
a reformat, so I might have a mate of mine who is into Linux give it a go as
a last ditch attempt.

Arfa