Sideband #25: 64-Bit Address

A long, long time ago on a USENET far, far away, I was part of a debate that started with the idea that, even if we had disk drives with 64-bit addressing, people would still fill them up with videos, images and whatnot. The idea grew from some of us old-timers reminiscing about our first brick-sized 5-meg hard drive and how we thought, “Gee, I’ll never fill that up!” (And look how that turned out; I have single image files that wouldn’t fit on that drive!)

The premise was that, even with seriously gigantic hard drives, we’d still manage to fill them and need more, more, more. And a couple of my computers with many hundreds of spinning gigabytes are showing much less free space than not. On the other hand, hard drives currently are in the terabyte range, which seems very spacious (I haven’t come close to filling mine). Plus there is cloud computing, which removes the burden of storing your own data, and there’s the idea of streaming video and music rather than owning it. This all appears to, perhaps, put an end to the tendency to fill the available space. Or even need much of it.

So it may be moot now, but a dozen years ago it was a debatable point (this was USENET; everything was a debatable point) that even a drive with 64-bit addressing might end up being not enough. We’ll leave off the detail that disk space is never actually addressed at the byte level, but at the sector or cluster level, so the available bytes are actually quite a bit more than the address space suggests. It turns out to be a detail of no significance.

Given the see-saw history of storage filling and capacity growth, it did seem possible. Until one really looks at the numbers. (In fact, I wrote my own arbitrary-precision calculator decades ago for the very purpose of exploring such topics.)

With 64 bits, you can count to 18,446,744,073,709,551,616. The size of that number alone should give you pause. It’s beyond terabyte, beyond petabyte, it’s 18+ exabytes! And while large data storage organizations might need that kind of storage, it seems rather a great amount for any individual.

Still, five megabytes seemed pretty big once, and each jump in storage seemed to offer an all but unfillable wealth of space, but each time we did find ourselves wanting more, more, more. So it’s possible that 18 exabytes might somehow be too much for an individual user with a passion for owning movies.  Let’s run some numbers.

I started by considering a very long movie: Gone with the Wind. It runs 238 minutes; nearly four hours. (This was before Lord of the Rings or other long epics came out.) I bumped that up to just over 4.5 hours to give me a nice round 16K seconds per movie. I assumed a frame was 8K pixels by 4K pixels (which at the time seemed ultra-high fidelity). I also assumed 32-bit color, 60 frames per second and eight-channel, 24-bit audio with a 96 kHz sample frequency.

This gave me 131,979,144,069,120 (uncompressed) bytes per very long movie. That’s nearly 132 terabytes for a single movie. You might think you could fill up an 18-exabyte disk pretty easily at that rate.

You’d be wrong.

It would take 139,770 movies that size to fill your disk. And they would take you over 600,000 hours (72.6+ years!) to view. And that’s assuming you could watch 24 hours per day, every day of those 70-some years.

I suppose you could fill such a disk (at least in theory), but what would be the point? For that matter, can you even imagine over 100,000 movies you’d want to see? (Forget the 100,000… can you imagine the 39,770??)

And there is the matter of exactly how you would fill it up. Downloading the data would be a bit of a problem. Assuming a 1-gigabit internet connection (125 megabytes) running full-out, each (uncompressed) 132-terabyte movie takes over 12 (24-hour) days. (If that seems improbable, keep in mind the movie we’re considering streams at a rate of 8 gigabytes per second. Stuff that down your Netflix streaming connection!)

Bottom line: filling your disk with the 139,770 movies would take 4,671 years!

Which all tells you something about the bit rate of real world information as well as the degree of data compression involved in our media.

About Wyrd Smythe

The canonical fool on the hill watching the sunset and the rotation of the planet and thinking what he imagines are large thoughts. View all posts by Wyrd Smythe

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