Snow Leopard Reports Hard Drive Capacity “Correctly” (in Base 10)

August 30, 2009

OS X capacity reportsZDNet reports that Snow Leopard has changed the way it calculates disk capacity from earlier versions of OS X: now it matches the advertised size of the drive you purchased it's actually accurate. When it's running Snow Leopard, your Mac shows you the same gigabyte count on your drives as appear on the manufacturer's box, calculated in base 10, and not in base 2, which is what Leopard, all earlier versions of OS X and all current and earlier versions of Windows uses. This Apple knowledge base article explains:

A 200 GB drive shows 200 GB capacity (for example, if you select the hard drive's icon and choose Get Info from the Finder's File menu, then look at the Capacity line). This means that, for example, if you upgrade from an earlier version of Mac OS X, your drive may show more capacity than in the earlier Mac OS X version.

My own tests confirm: a 4GB Cruzer thumb drive in my Snow Leopard Mac shows up with a capacity of 4.01GB. Leopard reports the same drive's capacity as 3.74GB. (Click to enlarge the screenshot on the right.)

Kudos to Apple for leading the charge on this change for the better, which will reduce age-old consumer confusion and questions about why a drive seems smaller in the software than it says it is on the box. This change also raises two other interesting questions: Is this new "found space" part of the reason why Snow Leopard "saves" you disk space? (Because if it is, SL isn't actually saving you anything--it's just an accounting adjustment.) More importantly for the rest of the market: When will Windows follow suit?

Update: All the passionate points about the difference between base 2 and base 10 are well-taken. I've updated this post to put the word "correctly" in the headline in quotes. The base 10 calculation change is "correct" as per consumer perception--i.e., I bought a 500GB backup drive and my operating reports that there are 500GB free, which is exactly what I'd (reasonably) expect. Right now the base 10/base 2 difference is totally confusing to regular people. Software does indeed use base 2 computation, but as far as I'm concerned, reducing human confusion is more important. The possibility that this change will increase confusion for folks who now won't get the same file size and usage stats across operating systems is a valid one; it will be interesting to see how it shakes out.

I’m not convinced this is a good move on Apple’s part as it may cause new confusion is people move back and forth between a Mac and Windows. Are file sizes also calculated using base 10? Also, in the picture you posted for this article, did you move the flash drive from a Leopard to a Snow Leopard machine without making any changes to the flash drive? The number of bytes used on the drive appears to be different which shouldn’t be affected by changing from base 2 to base 10.

ZLoether [+17]
Aug 30 09 at 5:30 pm

I don’t think this is a win for consumers. It’s a win for storage manufacturers, that’s for sure. A win for consumers would be for drive manufacturers to use base 2 and be honest when marketing the capacity of their devices.

Daniel Bendig [+1]
Aug 30 09 at 5:37 pm

I agree with Daniel Bendig. I also doubt Linux Distros would follow suit.

In addition, “now it’s actually accurate” implies that reporting in base 2 is inaccurate which is completely false since computers are binary.

I guess I need to second guess your statements on TWIG.

Thomas Suckow [+1]
Aug 30 09 at 6:33 pm

I can’t understand why you’d laud this as something positive when it’s really a big problem for people like me.

I use plenty of programs to figure out how much drive space I will need for certain video projects, and now they will all give me inaccurate results.

Frankly, now Finder will lie to me about my hard drive space.

I understand if you personally like this change, but to champion it as ‘apple doing something right’ is just wrong. And if all that space everyone has back is

I agree with Daniel if Apple really wanted to do it right they’d just sell their hard drives with the correct numbers using the 1MB = 1024KB style base 2.

Somebody had to do it.

Call me ancient but on my 64K Apple //e I always understood that 64K meant that the highest memory address was actually 65535 and that the hexadecimal (base 16) equivalent was FFFF—trivial, inconsequential.

Computer Math should be a necessary requirement for a high school diploma nowadays.

Now, if I could just remember 128K’s equivalent…

glindfordsmith
Aug 30 09 at 7:32 pm

@ShadyPghGuy: yes, I saved a file (the screenshot of the drive info) to the thumb drive before I ejected it from the Leopard Mac and moved it to the Snow Leopard Mac, hence the different in-use numbers.

Gina Trapani [+195]
Aug 30 09 at 7:39 pm

@Joseph Mastantuono: Apple IS doing something right by speaking the same language as all hard drive manufacturers and making things less confusing and more consistent for users. IMO, as always.

Gina Trapani [+195]
Aug 30 09 at 7:43 pm

I think the issue is mostly wording. You make it sound like 1K = 1024 is unacceptable anywhere.

IMO:
Is it good for Mac’s target audience: Probably
Is it good for a hardware engineer doing bit bashing: Probably not.

Thomas Suckow [+1]
Aug 30 09 at 8:53 pm

Interestingly, iTunes still reports the base 2 size.

Jarrod Willard [+1]
Aug 30 09 at 9:41 pm

Given the other reduction in HD footprint from the Snow Leopard installation comes from the omission of the printer drivers I wonder if the actual OS is actually any smaller when compared on an apples-to-apples basis (apologies for the pun)?

When a bug is not a bug, “Snow Leopard fixes disk capacity bug”. Now Windows versions of files will always be smaller.

Richard Frisch [+3]
Aug 31 09 at 2:36 am

Apple is hardly doing the right thing. Hard drive manufacturers have been using base 10 forever simply for marketing reasons. 250 GB sounds better than the 232 GB you get in base 2 for your 250 billion bytes.

But Apple giving into the manufacturer way is not only annoying to those who understand the 1000/1024 distinction, but it comes at the worst possible time. With solid state drives becoming popular, we are finally actually going to be listing the real capacity of drives. A 256 GB SSD is now going to be shown in OS X as having more than 256 GB.

Apple made the wrong decision here.

Rudd Zwolinski
Aug 31 09 at 3:57 am

Gina, I too, find this a strange thing to champion. I guess, as a geek, I’ve long been annoyed by this storage-manufacturer chicanery. The introduction of base 10 as ANY MEASURE of binary storage was a screwball, dishonest maneuver to start. Joe consumer would never have been confused if not for this convenient “adjustment”. Something is either a certain size, or it is not (how’s that for binary?). I get that there’s confusion, of the “I’ve been short-changed variety”, certainly for me whenever time I plug in storage advertised as one thing, but it’s REALLY 7% LESS. Why should I EXPECT it to be what it says on the box? What am I crazy? Truth in advertising? I think Apple “reporting” the “real” size is them currying favor with storage manufacturers. Is it Apple accepting reality, or…Apple making people FEEL better about storage on an Apple (welcome to the RDF) ??? You could call it smart. I could call the whole thing total BS. So I am. Regardless…, thanks for what you do Gina – I really appreciate it.

weebeast
Aug 31 09 at 5:23 am

This only works if everyone follows. Someone had to be first. Either the Storage Companies, The hardware distributors and/or the OS builders. Apple started well, but they should have changed it all over the OS (say in iTunes too)

I believe, Gina, this is an ‘accounting adjustment’ Here are the numbers from my upgrade:

Before:
Capacity – 185.99
Used – 91.37
Available – 94.62

After:
Capacity – 199.71
Used – 93.54
Available – 106.17

So even though I ‘have’ 12GB more space, the accounting change was nearly 15GB and my ‘used’ space increased by 2.2GB.

I assumed from Apple that maybe the operating system was 7GB more efficient. Maybe not…

Mitchel Laman [+1]
Aug 31 09 at 10:14 am

Fantastic discussion here folks, thank you. I’ve updated the post to clarify; I should not have used the word correctly without qualifying. Thanks again for all your educational feedback.

Gina Trapani [+195]
Aug 31 09 at 11:50 am

Here are some other results I found:

http://mlaman.wordpress.com/

Mitchel Laman [+1]
Aug 31 09 at 12:07 pm

I have to admit I’m with the general feeling of the commenters here. I think this is anything but a correction. It’s marketing over tech, and when I see it I feel like they’re stretching the truth, not making a proper a adjustment.

David Singer [+1]
Sep 1 09 at 7:51 am

Wait.. What! Why is this so hard? When I buy a gallon of milk, it’s not OK to get home and find out it’s “really” only 3/4 of a gallon. First I have to explain to my non tech friends why the hard drive they bought isn’t as big as the box says it is. Now I’ve got to try to explain why it won’t fit all the data on the drive that their Mac is telling them it should.

PLEASE just sell me a 931.322GB hard drive. Don’t call it a 1TB.

bobbismal
Sep 1 09 at 7:40 pm

Stick to your guns, Gina; “it’s actually accurate” is actually accurate.

That computers function in binary matters not one bit. In fact, the “binary argument” is fundamentally flawed, for several reasons:

1) Computers function in plenty of ways that shouldn’t be displayed to the vast majority of users: they fetch HTML/CSS but show a rendered web page; they read a pattern of real numbers yet play music; they calculate “2+2″ as 100, but answer “4″. Arguing for a particular display style, targeted at humans, because it more closely reflects the way the computer works is nonsensical. Computers are supposed to make things easier for people, not the other way around. Part of that should be displaying numbers that people really understand;

2) The international standard prefixes k, M, G, etc. are all defined as part of the decimal system, as the update to the ZDNet article so wonderfully points out. So 1,000,000,000 bytes = 1 GB, 2^30 bytes = 1 GiB. Apple is just being consistent with international standards, which is a good thing;

3) The set of digits before the prefix is a decimal number. The units prefix, as a multiplier to that number, should match. (Reading about the Mars Climate Orbiter will, by analogy, tell you why mixing systems is bad.) If the number were displayed in base-2 form as well, I wouldn’t imagine there’d be many complaints about a switch to something more human-friendly;

4) Regardless of how many slices you cut them into, a thousand pizzas is still a thousand pizzas. No one is seriously going to refer to them as 4.63 kilopizzas (1000/(6*6*6)) if they happen to be cut into six slices. So why call 500 billion bytes “465.7 gigabytes” just because of the way computers work internally?; and besides

5) Bytes aren’t binary; bits are.

I think this is a huge improvement. If it causes confusion in the short term, it’s not the fault of Apple now or hard drive manufacturers, but by all those who should have switched years ago, when computers first started to be used by people other than ubergeeks. If everyone else follows suit, this’ll be a non-issue.

Marc
Sep 3 09 at 3:52 am

All this shows is that Apple is conforming to human ignorance. Computers are binary machines, they compute math in binary as well display graphics on your monitor in binary. The real victory would be the media manufacturers to start reporting disk sizes in base 2 conformity not base 10. Just another way marketers are sticking it to the consumer.



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