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I need to update a particular sector in SD card twice in a second. In that case, I would be writing in a particular sector for 86400 times for 12 hours. Will this cause sector to wear out so fast?

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A buddy of mine burned out a bunch of SD cards in a few hours each. He was in an embedded systems class and tried to use SD memory as swap/virtual memory. – George P. Burdell Mar 23 '11 at 11:50
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twice a second seems a bit extreme for continuous use. It may be better use a different application, or get the application changed to spool the changes in system memory. – Rowland Shaw Mar 23 '11 at 12:12
If you are using the SD to achieve some kind of non-volatile storage of one single bit of data this sounds like a usage pattern that is suited for something like Ferroelectric RAM (en.wikipedia.org/wiki/Ferroelectric_RAM) rather than flash memory, as even with wear levelling I would expect you to kill any SD device within a few weeks. – Mokubai Mar 23 '11 at 12:24
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That depends on the SD card. A good one may reallocate the sector each time you write it to balance the wear across the whole card. A cheap one might even burn a hole right through the card writing that many times to the same sector in such a short time.

I would suggest using RAM and not SD for whatever you're doing.

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Can you provide a source for reallocation claim? Eveything I've seen says that the card itself does no reallocation and that it is implemented on a higher level. – AndrejaKo Mar 23 '11 at 12:11
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@AndrejaKo From en.wikipedia.org/wiki/Wear_leveling - "M-Systems' product DiskOnChip used a software driver named TrueFFS which performed wear-leveling of NAND flash chips and made them appear to OS like a conventional disk drive. On most contemporary flash memory devices, such as CompactFlash and Secure Digital cards, these techniques are implemented in hardware by a built-in microcontroller. On such devices, wear leveling is transparent and most conventional file systems can be used as-is on them." – Mokubai Mar 23 '11 at 12:31
@Mokubai Great! Does it work even when sectors are directly accessed using SPI? – AndrejaKo Mar 23 '11 at 12:47
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Normal expected lifetime of a flash memory sector is 10'000 writes, so it won't last even a single day.

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