Hard Drive Capacity Claims

[zodraz]

I've been doing the computer stuff since Mac 128s.

But something that has not been easy for me to find is why the difference in advertised Hard drive capacity and what you really get.

I know that there is some formatting that takes up space, (the diectory, desktop, etc).

But having gotten some very large drives lately, I see a that I'm REALLY not getting what they (manufactures) claim - by a lot!

Case-in-point, my OEM Apple 80GB drive shows up as 76.68GBs (Dual G4 mirror door).

And my brand new Western Digital 120GB drive shows up as having 111.75GBs.

That's a lot of Gigs I'm missin'!  

So, anybody have an answer?

Is there any "formula" for figuring this out?

If RAM can be sold as 512MBs and when you put put it in your Mac you really get 512MBs, why can't HDs do that?  

Thanks

     

[Jay]

I've always wondered the same thing!  It seems like the larger the hard drive, the more memory thats missing.

I hope someone has an answer  

Jay

[kelly]

Apparently there have been lawsuits over this.

http://216.239.41.104/mac?q=cache:NwjR0R7B...&hl=en&ie=UTF-8

Macintosh Hard Disk: Is It Missing Space?

http://docs.info.apple.com/article.html?artnum=30065

[Xairbusdriver]

It's a little known fact that the higher speed drives have even more of these problems. It seems that the faster the disk spins, the more bits are slung off. Since they are small, you seldom hear this happening. But anyone can see the results by looking at the amount of free space after using a HD for a while - it will inveriably have less space than when you first bought it!

Actually, every time you write something to the disk, you probably lose more space than absolutely required by the actual file. The disk is divided into a fixed sized sectors. Later OS's tended to make the size of them more constant instead of always the same number on any disk. But no matter what size they are, it is seldom the exact size of any particular file. So...when you format the disk you will automatically lose some space because of the information that gets written so the OS will know where all the sectors are. Then, when you install an OS, even more space is lost when each file gets a little more space than it needs for all those files. And don't forget that X creates a ton of invisible files as well.

Bottom line is that there are probably hundreds of sectors that have possibly Gig's of space that are unusable because they contain a small piece of a larger file.

Fix is to make sure than all files are multiples of whatever size the sectors are (usually 512, 1048, etc.) then, you will never have wasted space on the drive! Enjoy!

Reminds me of the Federal Budget! A few million here, a few million there... Before long we're talking big money!

[gmann]

If my pre AZ memory serves me, I believe the lose of bytes is due to Apple counting more bytes in a MB. I seem to recall 1024=1K, or some thing like that. Some one with the exact data should jump in here and correct my ramblings.

[Paddy]

Gary is correct - as the article Kelly referenced states:

"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 industry 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."

My 120 GB Western Digital formats out to 111.79GB - and if you do the math, 120GB translates to about 114.44GB. So, 2.65GB is lost to formatting. My IBM drive, which is 46.11GB according to IBM formats out to 42.95 GB, with about 1.02GB lost to formatting after you do the math to convert to Apple's figures.

So, all in all, about what one would expect. Bigger drive...more formatting.

[zodraz]

Thanks Paddy

I'll ask my kids to help me with the math!  

FYI, The first time I EVER turned this exernal drive on, (which was brand spankin' new) in OSX, (my daughters Powerbok) the computer said it detected an UNFORMATTED 111.79 GB drive, and did I want to format it.

So before a single bit of data was EVER written to the drive, or it even being formatted, the Mac was only seeing it as 111.79.

PS. I've been using it on my daughter's Powerbook and find that it's really zippy! I was editing in iMovie and was able to fly through a whole hour's worth of video by dragging the "playhead" back and forth. At work I hooked it to my dual G4 mirror door and copied 11GBs in around 10-13 minutes! Weeee!

Even my 7500 with Firewire card reads it quite quickly!