On Aug 23, 2014, at 6:56 PM, Duncan [off-list ref] wrote:

Zygo Blaxell posted on Sat, 23 Aug 2014 12:38:05 -0400 as excerpted:

quoted

Consumer SD cards are /terrible/ storage devices.  Always back up all
data written to an SD card as soon as possible after writing it, and
develop a process to restore the backup to a new SD card conveniently
when--not if--the card fails.

Over the years I've burned my way through dozens of SD cards in Pis,
Beagles, x86 laptops, USB SD card readers, cameras and cell phones.
I have more bad or failed cards than good ones in my collection, but no
more than three of any specific model.  Brand, price, and specs don't
correlate to success or failure.  Even the good cards wear out after
heavy use.  The bad ones fail much faster, and are more likely to give
you garbage data instead of properly formed I/O errors as they fail.

I had read that it was bad, but I didn't know it was /that/ bad.  The 
ones I've used have tended to be write-once, read for quite some time, 
often lose (or throw away as obsolete due to tiny size) before I write 
them again, or at least before I write them half a dozen times, and I've 
generally not has problems with them doing that, but I wouldn't tend to 
know about routine rewrite behavior.  Sounds like it's much worse than I 
might have thought.

Their primary usage is photography and video. Specifically it means highly variable camera firmware doing only sequential writing with only FAT32 (SD/SDHC) or exFAT (SDXC) as the fs, and jpeg, raw and video for file formats. The computer's job is pretty much read-only. It's a really narrow use case and I think they have their hands full with the camera firmware as a variable. So I wouldn't be surprised if the use case discussed here doesn't get much attention.

It's so bad for years now with CF and SD Cards the card manufacturer's say basically to expect corruption or malfunctioning cameras if you move the card between cameras without reformatting. And the reformatting needs to be done in-camera. In amateur and esp. pro photography and video, it's long been suggests to not delete individual files in the camera UI. Take your shots. When full or convenient copy all of them off the card. Back them up. Open/process them to make sure they're not already corrupted. Then reformat the card in-camera. Do the editing, i.e. delete photos you don't want, on the computer.


Chris Murphy