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The USB storage firmware itself will do this. ¼ was chosen to give a lot of space for this wear levelling to occur; wear levelling can't use occupied space, so it'd need to move data around a lot if the drive was close to full, which would increase wear.

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Wouldn't this also work with a large enough MicroSD?

As I understand it, the firmware for the majority of MicroSD cards is very limited. The physical size and low price point are likely the reason you don't see these more complex features in consumer cards. Also, if I recall, there's nothing in the spec about levelling so you'd probably get some half-arsed buggy implementation anyway.

Thank you for the clarification!

MicroSD cards tend to have much worse durability and IOPS than common USB sticks, and especially, say, an M.2 SSD to USB adapter.

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