[dr_zoidberg]

Largest sizes I'm finding for erase blocks are 128 and 256KB, not several MB. I am finding larger plane sizes, that probably comes from grouping more blocks together. In general, it's not massively different from what I described, it's just a difference in sizes involved at the higher levels.

[wtallis]

It still sounds like you're looking at tiny (≤4Gb) flash chips (or NOR?) for embedded devices, not 256Gb+ 3D NAND as used in SSDs, memory cards and USB flash drives. Micron 32L 3D NAND (released 2016) had 16MB blocks for 2-bit MLC, ~27MB blocks for 3-bit TLC. SK Hynix current 96L TLC has 18MB blocks, and even their last two generations of planar NAND had 4MB and 6MB blocks.

Having only 2 or 4 planes per die with per-die capacities of 32GB or more is a big part of why current SSDs need to be at least 512GB or 1TB in order to make full use of the performance offered by their controllers. 265GB SSDs are now all significantly slower than larger models from the same product line.