I know it's not a specific DM365 issue, but i have some understanding problems about the NAND Flash and i thought maybe someone can help me out:
The typical use case of our dm365 custom board will be:
* about 20 years of steady use aka "always on",
* reboots at least a 100 times in this 30 years
* very hard to access or maintain
* operation conditions not really friendly...outside ...-10 to 70°C possible...but at least no increased radiation ;)
So my concern now is how the NAND behaves over time.
What i "think" would be a good idea:
* Store UBL and Uboot redundant, since RBL and UBL check only on ECC. So if a block is bad, it will not be used from the beginning(initial or later re-/programming). If a block becomes bad during operation, we have at least n-1 copies. I assume that a block becomes bad or looses its data is very unlikely if you do not write/erase and only read!???
* With the Kernel and Filesystem I'm not sure: UBoot reads it from Block X with bad block management -> means it skips every block marked as bad and keeps on reading. So as long as no block gets bad during operation I'm fine because production-bad-blocks are also skipped at initial flash programming. Same question here: Can a block become bad or loose its data during operation if you only read from time to time? And here i can not store the Kernel and FS redundant, because there is no support in uboot for that, right?
In the data sheets they say the data retention they guarantee is about 10 years. So what does this mean? 10 years without or with power? operating conditions? What is a guarantee? I really do not find anything from the manufacturer that would answer this questions...
Would be great if someone could help me out here!
Valentin Ecker
