[hoek]

I just received my Pismo 500/20 and noticed in the profiler the drive is only reading 18.62GB capacity (with 17 available) and not 20. Where are the extra 1.38?

[Cipher13]

Formatting, and size translation.
The profiler will give two readings - size and capacity. Size will likely be closer to the 20, while capacity will be lower.
The reason for this is the 1 kilobyte is not 1000 bytes, but 1024. Just as a megabyte is 1024 kilobytes. And so on.
Get the idea?

Cipher13

[hoek]

Volume format: Mac OS Extended
Capacity: 18.62 GB
Available: 17.69 GB

Using the 1 kilobyte = 1024 bytes method, shouldn't my 20 gigabyte drive then = 20,480,000,000 bytes? Or is Apple saying that the drive is 20,000,000,000 bytes which is really 19.52 GB -- which is still more than 18.62?

I'm still confused as to my missing bytes. Are they floating around the dining room?

Apple (and ALL hard drive manufacturers, certainly the blame isn't on Apple) labels their hard drives in "Billions of bytes." Thus, a 20 GB drive is 20,000,000,000 bytes, as you correctly surmised. However, a real gigabyte is 1024 bytes * 1024 KB * 1024 MB, or 1073741824 bytes. Do the math, and that 20,000,000,000 byte drive is really 18.626 real gigabytes. That's where all your "loss" comes from, many people say "formatting" but in reality formatting takes up a few megs and is pretty insignificant.

[bookrat]

I never realised that. Thanks Scott. I always thought it was 1024 x 1000 x 1000.

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[uberden]

The Apple TIL that tells it all:

Hard Drives: Partition Size and Missing Space Explained



[This message has been edited by uberden (edited 01-30-2001).]

Actually, that Apple TIL is old and clearly outdated. Apple does no such practice anymore. The full and complete explanation for this "loss" of space is as I described, simply a difference in labeling of a "gigabyte." It has little or nothing to do with formatting.

[uberden]

Yeh, you're right. Updated November 11, 2000 is old. By what, a couple of months? What it also contains is a link to Macintosh Hard Disk: Is It Missing Space? which explains it as you did. To quote;

"At present, the hard disk drive industry measures disk capacity as 1MB = 1,000,000 bytes (1000 * 1000) . For example, this is defined in Quantum, Seagate, and Western Digital's product specifications and documentation (this is becoming an industy standard). For more information, visit these companies' respective web sites. The Macintosh Finder measures disk drive capacity as 1MB = 1,048,576 bytes (1024 * 1024). With regard to the above example, the 4 GB hard disk included in some Macintosh computers has a total of 4000776192 bytes of storage capacity. By industry definition this is a 4 GB hard disk.

The Mac OS Finder shows this space as follows if you divide the total bytes by 1,048,576 bytes: 4000776192 bytes = 3815.4375 MB = 3.7 GB

The disk drive industry measures drive capacity as follows if you divide the total bytes by 1,000,000 bytes: 4000776192 bytes = 4000.776192 MB = 4.0 GB"

I try to show people that there are ways to look up this information.
(my keyboard is getting flakey)




[This message has been edited by uberden (edited 01-30-2001).]

The talk about 120MB hard drives isn't very relevant to modern drives. On the other hand, I missed the reference at the bottom to the other TIL, which *is* applicable to this situation. Sorry about that.

The other 1.38 we cheated you out of helped to pay for Steve's Jet . . .

[Dan Szwarc]

I think that hard drives should be labeled in giga-BITES, not gigabytes. That explains the "lost" space.