Comment by mhh__

tPROG is time it takes to program a NAND page from when you put the "program page" command on the pins to when you read off a successful status.

Some of the basic NAND guides they put out are simple enough to understand the basics of operation

https://www.micron.com/-/media/client/global/documents/produ...

The details get very complicated and proprietary. NAND wears out as you use it. But it also has a retention time. It gradually loses charge and won't read back if you leave it unpowered for long enough. This is actually where enterprise drives can be speced worse than consumer. So durability / lifetime is specified as meeting specified uncorrected error rates at the given retention period. The physics of NAND are pretty interesting too and how it translates into how a controller optimizes these parameters. Temperature at various stages of operation and retention changes properties, time between erase and program does too. You can adjust voltages on read, program, erase, and those can help you read data out or change the profile of the data. Reading can disturb parts of other pages (similar to rowhammer). Multilevel cells are actually interesting some of them you program in passes so that's a whole other spanner in the works.

I don't know of a good place that covers all that, but much beyond "read/program/erase + wear + retention" is probably beyond "what every programmer should know".

The way you turn a bunch of NAND chips that have a "read/program/erase" programming model into something that has a read/write model (the flash translation layer or FTL) is a whole other thing again though. And all the endurance management and optimization, error correction... Pretty fascinating details really. The basic details though is that they use the same concepts as the "log structured filesystem", turns out a log structure with garbage collection is about a perfect it for turning the program/erase model into a random write model. That's probably what every programmer should know about that (assuming you know something about LSFs -- garbage collection, write amplification, forward and reverse mapping schemes, etc).