Example: most SSDs increase 1, 2, 4, 8, 16, 32, 64,…
In: 2
Most human cultures like to describe things in “powers of 10” because the *decimal* number system caught on really well and we like it that way. This ends up meaning that nice “round” numbers end up being things like 10, 100, 1000… or billions or trillions, etc.
Computers, however, are built to think in *binary* which makes “powers of 2” (like 2, 4, 8, 16, etc.) the nice “round” numbers for computer systems.
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The reason that matters when it comes to companies choosing SSDs sizes and whatnot is because – even though customers might prefer a nice “round” decimal number – the hardware itself is designed for the *binary* that computers speak.
To store a file, your computer essentially has to know the “street address” of every single “bit” of a file when you go to put something onto the SSD and/or read it later; when you “open a file” your computer is essentially saying “All right, this file says it is stored from address-0123 up to address-4321, let’s take a look and copy that all to RAM.”
So, the people who make SSDs essentially have to design a “post-office” capable of understanding all of the “street addresses” that the computer will end up using to deliver mail to/from those addresses. If you build a SSD with, say, 50 addresses… then you at the very least need a “post-office” that can understand addresses from 01, 02… up to 50… but that same post-office design is likely able to handle any other 2-digit address… anything from 00-to-99. But what if you need 150 addresses? Well, that’s too many addresses for a 2-digit (00-99) “post-office” to handle, but a 3-digit (000-999) “post-office” could handle it no sweat! But that means that 150 address is a bit of a waste when you’re already set up to handle 999… so why not just tell the guys building the roads to put in a few more mailboxes?
That same process happens with actual SSD design… except, because computers think in *binary* the street addresses look a little different. Instead of counting as (decimal) 0,1,2,3,4,5,6,7,8,9,10,11,12,13…you get something like (binary) 0,1,10,11,100,101,110,111,1000,1001,1010,1011,1100,1101… In effect, this means that *binary* “post-offices” get 2x as many available addresses every time they upgrade to handle one extra digit in the address. (As compared to the *decimal* post-offices in the previous paragraph which got a 10x improvement.)
So, essentially, SSDs grow as “powers of 2” because *binary* “post-offices” grow as “powers of 2” and adding more mailboxes is relative cheap/easy* to do if you already have a “post-office” that can handle it.
*(At other periods in time, other design constraints meant that “adding-more-mailboxes” wasn’t always plausible at the right consumer pricepoint. For example, in things like HDDs (for a certain combination of recording-head and spinning-platter technology) could maybe only fit so many mailboxes so tightly on a platter and so we end up seeing things like a 7TB HDD even though the post-office built for that HDD could handle 8TB.)
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