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What happens when the flash wears out?

How does a system with a worn-out flash behave? I know this is an overly-broad question...

I've got a Linux system running ext3 on an industrial CF card. I've pared the unneeded system activity down and I'm estimating that the CF in this application should last more than five years (based on vmstat

-d write counts).

So in the meeting I said we'd probably want to visit our field instalations after five years and replace the flash cards. And they asked "how can we really tell if the flash is worn out?"

Um - good question.

So, what happens with a worn-out CF card? Do writes actually fail with an I/O error, or is the data just garbled or lost? Does it hang, timeout? Do reads report CRC errors, or silently return incorrect data? Is it dependent on CF vendors, product types, etc? Is there a (non-destructive) test that will tell you if a card is worn out?

Reply to
Richard Krehbiel
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Reads report CRC errors on the cards I've tested to destruction. If you're lucky. In a worst case, the card will just stop working altogether (I've observed this happen on a couple of Chinese cards, a long time ago, when they ran out of spare sectors).

Reply to
larwe

On the lowest (hardware) level, you get read errors and write failures. How these are propagated through the OS is an entirely different question. As to diagnosis, I'd expect the write time on bad cells to slowly increase, and I would expect read errors on sectors to create ocasional CRC errors before failure. Since an OS possibly never has access to such data, it'll be hard to do with the OS alone.

Rene

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Reply to
Rene Tschaggelar

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