On Fri, 2009-02-06 at 07:11 +0000, Stroller wrote: > On 6 Feb 2009, at 05:28, Iain Buchanan wrote: > > It's a Lexar Media 512Mb SD card, a couple of years old. Yes I know I > > can get a cheap 2Gb for <$20 but I'm more interested in the > > principle of > > the test :) > > I thought you could get then for < $5, but anyway....
probably in USD. We (AUD) were approaching 1.00 before the exaggerated crises, but now we're back to 0.645; and plus I needed one in a hurry, so I couldn't order from a PC store which has reasonable prices and instead had to go for a local and slightly more expensive retailer... > > so I created a file: > > dd if=/dev/urandom of=Desktop/random.img bs=1024 count=500960 > > > > then copied it to the card, and then copied it back as > > random-2.img. If > > I md5sum the two files, they are identical: > > $ md5sum random* > > 9dcac25cfd8585be5939c0ff969de310 random-2.img > > 9dcac25cfd8585be5939c0ff969de310 random.img > > > > Does that mean my memory card is good to go, or should I use some > > other > > method of bad sector detection? > > I'd be more or less happy with that methodology, had I copied a > thousand files to the card & they checked out good. > > Of the top of my head I don't know how big your "bs=1024 count=500960" well, I got that from the free space on the card, using df and some mathemagics, so it 100% fills the free space... however... > file is - I would make a Bash script generate files c 5meg in size > (maybe alternative between 3meg & 6meg?) and copy them to the card > until it fills up. Then check them, delete them and do so again until > all 1000 have been copied & checked. [snip] however my method and your suggestion only fill up the free space, and not the FAT for example, so there could be corruptions there, and given I could see files but the names were nnnxxnnxnnn.ddxxc and so on, I think it could have been a corrupt FAT?... I should have made a file the size of the whole SD card, and just written it to and read from the device a couple of times, overwriting the partition table, and FAT. > Personally, for my money, I don't know if I'd trust it. Depends what > you're storing on it. MP3s for my phone? Sure - I have a backup at > home. Moving files onto my PS3 or Wii, sure. For my camera? Maybe I'd > be a bit cautious. Bought a new 2Gb. Unfortunately I want a 512Mb card cause then I'm forced to back it up often enough. -- Iain Buchanan <iaindb at netspace dot net dot au> Men have a much better time of it than women; for one thing they marry later; for another thing they die earlier. -- H.L. Mencken