If I saved 1 byte of data on a USB drive, theoretically, would you be able to take apart the USB drive and point to where the 2nd bit of my single byte is? And if it is 0 or 1?
In: Technology
A USB flash drive typically uses NAND storage, which is an array of cells, where each cell holds one bit of data. These are usually organised in blocks in a certain way, so if you’re familiar with the layout, you could figure out which cell holds the bit you want, and then probe it to check whether electric current flows through that cell, which tells you if it’s a 1 or a 0.
A cell is made out of a transistor, which is a sort of switch that only stays on for as long as you hold it. It’s like those public-bathroom sinks with auto-shutoff valves where you can only wash one hand at a time.
In flash storage, we *jam* that switch open to keep it from turning off automatically. Even when the power’s off, the switch stays in whatever position we last jammed it into. Then we add another switch that controls the jammer. Unfortunately this eventually breaks the valve and it typically gets stuck wherever we last put it, which is how SSDs wear out over time.
The “jamming” is putting an oxide wall around the gate of the transistor, so electrons can’t escape, and charging it up or discharging it *through* that wall using huge voltages and quantum tunnelling. So, in the sink-valve analogy, it’s a bit less like a wrench and more like a magnetic wizard.
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