Harddrive Question? 120 GB to 111GB?

No, this is perfectly expected behavior of most harddrives on any system. Harddrives may hold 120gigs but depending on how they are formatted and their block size, the software can show sizes that vary slightly from the actual. Plus some operating systems borrow memory that you might not be seeing.

For example, with a lot of fragmentation very small files or very small parts of large files may take up an entire block that they don't need. In this case, the disk usage looks worse than it is.

No need to worry, its running as it should.

When a hard drive capacity is listed as 120 GB, they mean 120 times 1 billion bytes. (There's a footnote to this effect on the Technical Specs page.) When you check the capacity in Mac OS X, it uses GB to mean 2^30 (i.e., 1024 times 1024 times 1024) bytes or 1,073,741,824 bytes. In that notation, 120 billion bytes, which is the quoted capacity of the disk, displays as 111.76 GB.

There was a class action suit about this a long time ago. One of the consequences of the suit is that the hard drive manufacturers now make it clear that when they say GB, they mean 1 billion bytes.

So you won't be confused by the two different replies you received, the one by Gary Palter is correct; the one by ApolloX is incorrect. Give Gary the points for solving your problem.

Gary is correct indeed, and so is Kappy for saying so.
(there is 73,741,824 bytes missing in what the manufacturers consider a GB... that or there's 73,741,824 bytes too many in what the computer considers a GB to be - unlike us, it thinks in binary, which is at the root of this misunderstanding. i.e. 2x2 never makes 100, 1000, 10000 etc. 8bit, 16bit, 32bit, 64bit... get it? Think ram: 128, 256, 512... 1g ram is like... 1024meg ram... (check your Activity Monitor))
all these little bytes we overlook eventually add up!

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Ummm thats not true. The reason the size is that way is because of the encoding of a block when the drive was formatted. Please do not post incorrect information.

Michael,

Just to put it another way for you and re-enforce Gary's reply.

In brief, when you see HD capacity adverised as 60GB, 80GB, 100GB etc, that's the marketing way where they take "decimal" road and base 1GB as being equal to 1,000,000,000 bytes. This is true for all HD manufacturers and computer manufacturers.

Once upon a time, computer professionals noticed that 1,024 bytes (binary) was very nearly equal to 1,000 (decimal) and started using the prefix "kilo" to mean 1,024. That worked well enough for a decade or two because everybody who talked kilobytes knew that the term implied 1024 bytes. But almost overnight a much more numerous "everybody" bought computers, and the trade computer professionals needed to talk to physicists and engineers and even to ordinary people, most of whom know that a kilometer is 1000 meters and a kilogram is 1000 grams.

Often when two or more people begin discussing storage capacity, some will refer to binary values and others will refer to decimal values without making distinction between the two. This has caused much confusion in the past (and still does). In an effort to dispatch this confusion, all major disc drive manufacturers use decimal values when discussing storage capacity.

Some simple arithmetic will convert the advertised (decimal) capacity to the actual (binary) capacity ;-):

1KB = 1,024 bytes
1MB = 1,024 x 1,024 bytes = 1,048,576 bytes
1GB = 1,024 x 1,024 x 1,024 bytes = 1,073,741,824 bytes

Therefore, in your specific case:

120GB (decimal) = 120 ÷ 1.073741824 = 111.75870895386 GB (binary or actual capacity)

Rounded off to two decimal points = 111.76 GB

I hope this clarifies it for you and explains the reasons for the discrepancy.

RD

ApolloX, you are answering a question that hasn't been asked! 🙂

If the question had been in relation to having 111GB of data take up 120GB of space on a HDD then yes you are right. The query was about why an advertised 120GB HDD is only 111GB though.

Red Dwarf: Great explanation, maybe we should reference to this one, when the question comes up again. And I'm quite confident it will come up again

Thats all fair and good but I noticed that as soon as I started up my macbook pro for the first time the space available was 87.23 GB which is a lot of lost space. Where the **** did it all go? I didn't add anything to the disk it was like it as I had bought it.

Any help would be greatly appreciated