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If data is actively being written to a flash memory device, can a memory cell (or perhaps the entire memory device) be physically damaged if power is removed, or will data simply be corrupted? Can the affected device or memory block still be written to and read from (even if the data itself is corrupted)?

This question has been on my mind since I've encountered memory cards for video game consoles where the manufacturer claims such damage would occur in the event the power is turned off while saving, and it still bothers me with regard to USB flash drives and SSDs.

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up vote 8 down vote accepted

Here is a paper about errors caused by power failure on flash memory: http://cseweb.ucsd.edu/users/swanson/papers/DAC2011PowerCut.pdf

I cite the last sentence of the abstract:

Finally, we show that incomplete erase operations make future program operations to the same block unreliable.

and the conclusion of the paper:

The flash memory devices we studied in this work demonstrated unexpected behavior when power failure occurs. The error rates do not always decrease as the operation proceeds, and power failure can corrupt the data from operations that completed successfully. We also found that relying on blocks that have been programmed or erased during a power failure is unreliable, even if the data appears to be intact.

My personal conclusion is

  • Power loss in general can render flash memory in an unreliable state. However, once you hard erase, the memory works as good as before.

  • Carefully written firmware can fully prevent errors on power loss but at a performance and lifetime cost of the flash memory as writes have to be protected by extra writes.

  • Many vendors offer hard erase utilities for download. But I think there are flash memory devices that do not allow you to do a hard erase and also will not perform a hard erase themselves and also do not employ a perfectly safe write protocol. It follows that these can be rendered effectively unreliable or unusable by power loss during a write even if they are not damaged physically.

  • If you really want, you can take an "effectively unreliable or unusable" USB memory and move (i.e. desolder and reconnect) its flash ICs to an environment that allows hard erasure. The flash ICs should be useable again now.

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I added my conclusion which addresses your question directly. –  Peter G. May 30 '11 at 6:44
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If the power is interrupted, there will not be any damage to the memory block. If there were a surge of some sort it may happen, but simply removing power will not damage the block itself.

There his a chance that the file system may be corrupted, depending on the firmware of the drive in question, it may have issues with the file system / table corruption and may need to be erased with a utility provided by the manufacturer (if they do), it appears that some corruption may possibly lead to a drive that is not reliable, but usually that is due to firmware rather than the NAND failing.

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