by bigiain | 2025-11-11 23:44:32+00:00
Dans Data (RIP that website, apparently) did this backup tapes to microSD cards update about 15 years ago.

He started with "Well, first we need to know how big our station wagon is. I hereby arbitrarily declare it to be a 1985 Volvo 240, which has 2.2 cubic metres of cargo capacity." and "I'm also going to assume that the wagon isn't really packed totally full of memory cards, such that they cascade into the front whenever you brake and will avalanche out of the tailgate when it's opened. Let's say they are packed almost to the roof of the car, but in cardboard boxes, which reduce the usable cargo capacity to a nice round two cubic metres."

The calculated "Assuming uniform and perfect stacking of objects of this volume, with zero air space, you can fit 24,242,424 of them into two cubic metres."

But he also addressed the packing problem, saying:

"In the real world there'd obviously be air spaces, even if you painstakingly stack the tiny cards in perfect layers. My size approximation, that ignores the more-than-0.5mm height of the thick end of the card, could make the perfect-layers calculation quite inaccurate. But if you're just shovelling cards into the boxes and not stacking them, though, there will be even more empty space between cards, and the thicker ends won't matter much.

To use a few words you may have to hit Wikipedia about - I know I did - a random close pack of monodisperse microSD-shaped objects will be considerably tighter than one for, say, spheres. I wouldn't be surprised if it only reduced the theoretical no-air-space density by 20%, provided you shake the boxes while you're filling them.

So let's stick with a 20% density reduction from random packing, giving 0.8 times the theoretical density of perfectly-packed cards. Or nineteen million, three hundred and ninety-three thousand, nine hundred and thirty-nine cards, in the boxes, in the station wagon."

He was writing in 2015, and settled on 16GB cards and being reasonable, getting 275 pebibytes. If we switched them to the 1TB cards mentioned upthread that'd be 17 exabytes in a 2 cubic meter stationwagon cargo area, or in a 67 cubic meter shipping container you'd get 575 exibytes. And that's the "load with a shovel and shack to pack down" number, so perhaps 720EiB if someone took that forever to carefully pack them.

Your 100 tons problem is real, it seems shipping containers (both 20 and 40 foot) seem to top out with a cargo payload of 28 tons. So let's call it "only" 161EiB shovel loads.

The font of all hallucinations and incompetent math tells me "The total amount of data on the internet is estimated to be around 40 zettabytes as of 2025, which is equivalent to 40,000 exabytes." So you'd only need 250 shipping containers or so to store a copy of the entire internet. And that's barely 1% of the capacity of a modern large cargo ship. I guess for reliability you'd use 500 shipping containers in redundant mirrored RAID1 config, each half travelling on a different ship.

Dan also noted: "Unfortunately, even if your cards and card readers could all manage 50 mebibytes per second of read and write speed, getting all of that data onto and off of the cards at each end of the wagon-trip in no more than 24 hours would require around 68,400 parallel copy operations, at each end."

That works out to 2.3 million readers for one parallel copy of one containers worth of data in one day. And 570 million for 250 container's worth.

https://web.archive.org/web/20250313181659/http://dansdata.c...