[Coco] CF and SD life expectancy

[Bob Devries]

Interesting. Cross posted from the BBC-Micro mailing list.

QUOTE:
Most of the consumer-grade CF and SD cards you can buy today are probably 
using MLC flash which requires fairly careful supervision if you want your 
data to stay intact.  In particular, each block of MLC can only be read from 
a certain number of times before it needs to be erased and rewritten. 
There's also the wear-levelling issue which is more severe with MLC because 
the write cycle endurance of each block is less than SLC by about a factor 
of 10.

That's not to say that it's necessarily impossible to make a reliable card 
out of MLC, but it requires a fairly sophisticated controller and my 
experience has been that a lot of the lower-end cards either don't have the 
right level of technology for that, or haven't been appropriately tested and 
don't actually work correctly.  On some of the cards we tested recently at 
work, just reading from the same file a couple of thousand times would cause 
the data to gradually become corrupt.
/QUOTE

Remember that NitrOS9 reads the first sector and the File Allocation sectors 
*frequently*.

Regards, Bob Devries
Dalby, QLD, Australia