> John Conover (12022-12-26): > > So, the more unused SD space is better, since wear leveling writes > > to a "bit" that has been written to fewer times. > > > > To test, say with a 16 GB SD, fill the SD to all except the last 1 > > KB, and with a looping script, write 1KB of 1's to the remainder of > > the SD, erase the "bits," then 1KB of 0's, erase the "bits", and so > > on; the SD card will fail within hours to a few days, (with > > luck-note that MTBF is mean time between failures, meaning that by > > MTBF, half will have failed, half still running; its a > > stochastic/probability issue; it does NOT mean that all are > > expected to last at least 6K writes.) > > > > Doing the same test without filling to the last 1 KB, and the SD > > card will last a very long time, (about 16 million total writes.) > > Are you suggesting that the microcontroller of the SD card is capable > of decoding filesystem data structures to find out which sectors are > unused? > > I find it rather surprising. > > That implies a SD card could discard data from deleted file, defeating > recovery tools and steganography. > > If find it highly doubtful.
Perhaps you might want to read what e.g. wikipedia says about wear-levelling before drawing too many more apparent conclusions about how it works, what the conseqiences may be, and John's credibility? :) > Regards, >
