In article ,
John Keiser wrote:

This is slightly off topic but perhaps you will indulge me.
I have a cheap 8GB "no name" flash drive. It formats and seems to behave
properly. I copied 1.5 GB of photos onto the drive. Some of the .jpg are
readable, but some are not although they are readable on the harddrive.
I tried reformatting, etc, but same issue occurs.
I can't really trust the flash drive.
Any suggestions on how to remedy and verify?
Thank you.

An unfortunately high percentage of "high-capacity" no-name flash
drives are bogus. They actually have smaller storage capacities, and
their controller chips have been deliberately programmed to report a
false capacity. Accesses to sectors falling beyond the device's
actual storage boundary will often "wrap around" in an unpredictable
fashion, overwriting existing sectors with new data. The result is
just as you have observed - corrupted files.

This sort of falsification is often not detected by an operating
system's normal formatting routine, since formatting doesn't require
writing to more than a very small fraction of the sectors in the
filesystem.

In order to detect such forgeries in a definitive way, it's necessary
to write a unique pattern to each individual sector (e.g. fill each
sector with its own sector number), then read back every sector and
see if it has the right unique pattern in it. An honest drive will
past this test; a dishonest one will fail, and you'll be able to see
which sector's data clobbered which other sector.

From the behavior you report, it sounds as if you may have a 1-gig
drive, relabelled and reprogrammed to appear as if it were an 8-gig
drive.

Such counterfeit drives are not uncommon on eBay and similar online
auction sites, at electronic flea-markets, and so forth. It's best to
buy high-capacity drives from reliable local sources, and then test
the drives to confirm their legitimacy - and if they fail, take 'em
back to the store and raise a stink.

Remember, "cheap" is often very expensive.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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