Comment by throwawaylinux

It's called the program-erase model. Some flash devices do expose raw flash, although it's then usually used by a filesystem (I don't know if any apps use it natively).

There's a _lot_ of problems doing high performance NAND yourself. You honestly don't want to do that in your app. If vendors would provide full specs and characterization of NAND and create software-suitable interfaces for the device then maybe it would be feasible to do in a library or kernel driver, but even then it's pretty thankless work.

You almost certainly want to just buy a reliable device.

Endurance management is very complicated. It's not just a matter of PE cycles for any given block will meet UBER spec at data retention limits with the given ECC scheme. Well, it could be in a naive scheme but then your costs go up.

Even something as simple as error correction is not. Error correction is too slow to do on the host for most IOs, so you need hardware ECC engines on the controller. But those become very large if you have a huge amount of correction capability in them so if errors exceed their capability you might go to firmware. Either way, the error rate is still important to know the health of the data, so you would need error rate data to be sent side-band with the data by the controller somehow. If you get a high error rate, does that mean the block is bad or does it mean you chose the wrong Vt to issue the read with, retention limit was approached, the page had read disturb events, dwell time was suboptimal, operating temperature was too low? All these things might factor in to your garbage collection and endurance management strategy.

Oh and all these things depend on every NAND design/process from each NAND manufacturer.

And then there's higher level redundancy than just per-cell (e.g., word line, chip, block, etc). Which all depend on the exact geometry of the NAND and how the controller wires them up.

I think better would be a higher level logical program/free model that sits above the low level UBER guarantees. GC would have to heed direction coming back from the device about what blocks must be freed, and what the next blocks to be allocated must be.