160GB but only Total Capacity : 149.1 GB ???

M

Mike6912

Registered
Good evening everyone,

my external HD LaCie 2d extreme has 160GB but if i click on disk utility i get the information that my disk has a Total Capacity : 149.1 GB (160'041'885'696 Bytes)

Also on Tech Tool i get the information
USED 46.96 Mb
Files: 5
Folders:4

but the disk should be empty

What am I doing wrong, do i have to format the disk and if how do i do this haven't found a format programm.

By the way i only have one partition i have checked this .


Thanks

Mike
 
There are too issues at work here:

1. Marketing bull. In marketing, 1GB = 1 billion bytes. Everywhere else, 1GB = 2^30 bytes (or 1,073,741,824). So 160 "real' GB is 171,798,691,840 bytes. And 160 "marketing" GB is only 149 "real" GB.

Note: To avoid this kind of confusion, some group decided to forfeit the term "GB" to the marketers and coin a new term for "real" GB, called GiB, short for gibibyte. But hardly anyone ever uses this (possibly because it sounds so darned silly), and its existence doesn't change the generally accepted (non-marketing) definition of GB.

Another note: Not ALL marketing uses the "marketing" definition. For example, 700MB CD-Rs can actually hold MORE than 700 "real" MB (702.8 to be exact). But those 8.5GB DVD+Rs you see only hold 7.9 real GBs. *sigh*

2. Formatting stuff. Even an "empty" disk will use some space for its databases and stuff. I think 46MB is within the normal range for this stuff. You could reinitialize it in Disk Utility, but you'd probably get a very similar result afterwards anyway.
 
Imagine buying 5 acres to build a parking lot, analogous to a (truly) blank 5GB drive. You could park cars in that undeveloped 5 acres, but it wouldn't be efficient; you'd have a hard time finding specific cars. Disks are much the same way. There might be 5GB of raw space, but you're gonna have to forfeit some of it for the sake of efficiency. Back to our parking lot. You decide that for efficiency's sake you paint lines on it. The would be similar to formatting a disk. The lines take up space, since you can't park directly on them, but it makes it a bit more efficient for both parking and finding a car. Formatting a disk puts "lines" on the parking lot with spaces reserved for blocks of data. Once the lines are painted, you can't use that particular space for your data. So once you paint lines on your 5 acres lot, you now only have 4.99 acres of usable space. Take more for signs and what not and you have even less. The mysterious folders and files on a "formatted" disk might be akin to signs such as "reserved."

That, friend, is a very generalized view of filesystems. I hope that helps your understanding.

-Jason

Mike6912 said:
Good evening everyone,

my external HD LaCie 2d extreme has 160GB but if i click on disk utility i get the information that my disk has a Total Capacity : 149.1 GB (160'041'885'696 Bytes)

Also on Tech Tool i get the information
USED 46.96 Mb
Files: 5
Folders:4

but the disk should be empty

What am I doing wrong, do i have to format the disk and if how do i do this haven't found a format programm.

By the way i only have one partition i have checked this .


Thanks

Mike
Click to expand...
 
yes i do understand it now.
thank you.
i was just worried that there is something on my disk which shouldn't be there.
The reason why i have bought the disk is to use it as a backup system and to store files which i don't need everyday on my PB.
So i was worried that my backup might get a problem, because of this.

Anyway thanks again

Mike
Lugano - Switzerland
 
In addition, to confuse the subject even more, there's actually data that exists on a hard drive even when it's completely blank -- for a 160GB clean-formatted drive, you'll notice (via Get Info) that there is 8MB to 20MB of space taken up by invisible format data.

I tell ya -- after I became a computer scientist, I quickly learned that just about everything done with computers is a "hack" or workaround (programs, code, hard drives, memory, etc.), and that the inner workings of computers aren't nearly as complicated as they seem. That's why we have situations like this.
 
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