Sounds like filesystem (metadata) corruption. Fist make sure that the device is working at all, dd_rescue is your friend: Overwrite the _whole_ device with zeros. dd_rescue /dev/zero /dev/sdx (find out what sdx should really be, see the output of the command dmesg after attachment of device). If any error occurs, bin the thing. Then read the whole device. dd_rescue /dev/sdx /dev/null If any error occurs, bin the thing. Partition (optional), and create a new filesystem. Enjoy. I do this for every storage device I use. Helps to sort out DOAs (which otherwise _appear_ to be OK until you use the majority of space; i.e., fail when it hurts most). Also sorts out fakes (more advertised space than actually there) and broken interfaces (sadly more common than one may expect). With flashy storage learn about MTBF, max. transfer per time, expected lifetime etc. beforehand 8^) Best, jj P.S.: hope you got a backup. * Henry Baker <hbaker1@pipeline.com> [Jan 23. 2015 08:50]:
(This question is also relevant to certain robots on Mars.)
I bought a number of questionable flash memory cards (formatted as FAT32), and I wasn't disappointed with their questionableness -- they're failing, so I've been trying to figure out their failure modes w/o having access to their internal management software.
They are showing bizarre failure modes.
The files don't seem to be failing in a single block, but the failures seem to be more global.
For example, a folder will cease being a folder, and look like a regular file, while the files in the folder can be recovered by file checking software.
I see almost no failures (= modifications) on files less than 100Mbytes, but nearly 100% failures on files >200Mbytes.
Has anyone else here studied flash memory card (uSD card) failures?
Is there any software on the internet that can pinpoint failures so that I can simply remove these blocks from consideration?
(I realize that it's cheaper to buy new uSD cards, but I thought it would be fun to understand the failures.)
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