I have used a 64GB TransFlash cars from SanDisk for over 1,5 years and now, after I wrote a large WAV file to it, it started to behave in a strange way:

all the files and folders on it are readable. If I write something to it or even delete a partition it pretends that operations were done successfully, but on next re-read or next card re-mount it turns out that the complete old state has been kept intact, no changes were made.

Is the card damaged permanently?

3 Answers 3


Maybe your card is a fake sd card, menaing that its capacity is fake : each write overlaps previously writes.

In this case, the real capacity is less than the capacity exposed by the card to OS.

There is several products to test real capacity. The principe is simple: this softs writes as many files as they can containing some random data. Then they read those files; and checks that the read data corresponds to previousmy written data (md5sum).

Many non open-source and windows-only (bad) softs exists, like those :

  • H2TESTW (the more often mentionned)
  • FakeFlashTest
  • Check Flash
  • (and maybe others)

Some open-source and multi-plateforms exists (goood !) :

  • F3 (my personal choice)
  • FileReadTest (I didn't test it, mainly because it's written in Java)

I noticed also the existence of a windows-only but open-source one : USB Memory Stick Tester (usbmst). Didn't tested cause I'm under Linux.


I would suggest copying everything on the micro sd to you hard drive and the FORMAT the micro sd (yes people say don't format sd or usb cards but its ok really ) I get the same problem as you and I sure its windows 8.1 being to security conscious. its the same as copying files from a to b in windows xp an windows 7 its pretty fast but windows8-8.1 is really slow

  • It restores it's contents after formatting.
    – Paul
    Sep 11, 2014 at 10:08

The right answer is: Yes, the card is damaged permanently. Probably some important memory cell is worn out, and the card pretends to be written and restores it's contents even after formatting.

  • 1
    If the card comes up as "read-only", then the controller in it has detected alarming trouble and therefore will not allow more writes - in an attempt to allow retaining the data there is.
    – Hannu
    Aug 23, 2015 at 12:01

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