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Comment by tiagod | Hacker News Reader

A DVD's surface area is around 134cm2. A microSD card area is around 1.65cm2. This means around 80 microSD cards in the surface area of a DVD. Multiplied by 2TB, the largest currently available microSD size, we get around 160TB, which is 1.28 Pb (Petabit).

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I find the inverse calculation interesting also with CPUs. I used to really enjoy NES games. Apparently its based on a MOS Technology 6502 that has ~3500 transistors on a 16.6 mm2 area.[1][2]

The most recent Intel CPU I can find is a Haswell-E with transistor data, at 2,600,000,000 transistors on a 356 mm2 area. [3]

I should be able to get an NES that fits on 22um x 22um in the modern era. Which, Wikipedia says is approximately the size of fog droplets, hair, or conveniently, the size of the original transistors in the Intel 4004.[4] I could breath NES CPUs and barely notice. Fog droplets.

[1] https://en.wikipedia.org/wiki/Nintendo_Entertainment_System#...

[2] https://en.wikipedia.org/wiki/MOS_Technology_6502#Technical_...

[3] https://en.wikipedia.org/wiki/List_of_Intel_Core_i7_processo...

[4] https://en.wikipedia.org/wiki/Orders_of_magnitude_(length)

My understanding is that SD cards are not good for even medium-term storage. They have to be powered on regularly or there's a good chance the data will be corrupted or lost entirely.

And most current optical disks rot - the layer written is usually in an organic coating and beyond that the glue holding the data layer(s) can break down over time. Magnetic storage has been the most reliable stuff I personally have used. Given I haven't sought out the 100 gold disks or anything.

Vinyls warp and scratch. Film degrades and becomes foggy. Books are damaged by too much moisture or not enough moisture. Most clay tablets have been smoothed by erosion.

Optical disk rot is an overstated problem. Every medium has longevity issues. I often deal with 25 year old CDs and old DVDs and they are fine if they were stored properly.

Whoah if that's true it should be more known...

it takes about 10 years @ 55c for the memory cells to start losing charge without being powered, people who use them extensively do know

for most other people it doesn't matter if they know because almost nobody uses SD cards for long term cold storage, and neither should they

I bet there are a lot of people with an old digital camera or two lying around with some photos on which they hope to look at one day. And if the same is true for solid state hard drives, we will probably find the same behavior with old laptops in about 5-10 year.

I think it depends on what we define as medium or longterm storage. Even 10 years of unpowered storage should be fine.

Interesting calculation. If you shave a bit of area from each microSD to remove connectors and such you’d probably be able to fit 10-15% more..

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