When Is A 300Gb HDD Not a 300Gb HDD

whiteboard

Just bought some new 300Gb HDDs. However, when I format them under xp pro they give 279.47Gb. Can anyone explain why I have lost the guts of 20Gb on each disk when they are formatted?

philologos

XP works under the fact that a GB is 1024MB
the drive works under the fact that a GB is 1000MB

Mutant_Fruit

HD manufacturers measure 1 kilobyte = 1000 bytes.
Windows measures 1 kilobyte = 1024 bytes.

Thats the difference between your 300gigs and 279 gigs.

Syth

Everywhere in computing measures 1 GB as 1,024 MB. It's only hard drive manufacters who choose to view 1 Gb as 1,000 MB. They all do it, so the company you bought it from didn't screw you secretly. They screw all of us.

This confusion caused the creation of new prefixes. 1 Gibibyte (or 1 GiB) is 1,024 MiB (Mebibytes), etc. Now if only everyone would just use it.

SouperComputer

Formatting also occupies space. You can free up more space by changing the cluster size. But its a risky business if you dont know what you are doing.

Capt'n Midnight

Also at the start of the disk there is a file index

at the command prompt type defrag C: -v to see other space XP uses (might have to wait a few minutes..)

1GB = 1,073,741,824 Bytes
1,000,000,000 Bytes = 0.931322574 GB

With a TB drive you will loose more - nearly 10%
1TB = 1,099,511,627,776 Bytes
1,000,000,000,000 Bytes = 9.094947 TB

It's only the HDD makers who do this, RAM / Video Cards / USB keys are fair enough

That Guy 901

With all storage devices its the same thing. My 1gb pro duo says 978mb!!

0utshined

And today we've learned a very important lesson : The marketing department should always be made run things by the engineering department before a product is launched .

RoyalMarine

didnt know that 1...
dam. i wondered that myself for a long time.

themole

so there are different ways of describing the size, fair enough.
either way the "usable" amount will always be less than the "actual" size of the device due to formatting.

The reason you "loose" space due to formatting is that when you describe the "size" of a storage device you are describing the number of "1's" and "0's" ie data, it can hold.

but to be able to store the data in a meaningfull way you need to format the drive, that is install a file system on it. the file system itself consists of data, "1's" and "0's" like all data, so it takes up some of the storage space.

so the amount of "usable" space on a drive is always less than the "actual" size of the drive.

the unformatted size is used to describe a drive because there are lots of different file systems which take up different amounts of space


its akin to storing paper files in a room.
you can throw then all in until the room is full, but the files will be hard to find later,
or you can put filing cabinets in the room and fill them.

either way the room is still the same size, but in the second case it will hold less files

po0k

So 278Gibs isn't quite enough space to hold your 300Gibs of donkey pron?

incisor71

whiteboard wrote:

Just bought some new 300Gb HDDs. However, when I format them under xp pro they give 279.47Gb. Can anyone explain why I have lost the guts of 20Gb on each disk when they are formatted?

One-word explanation: overhead.

themole explained it beautifully - the capacity 300GB is a little misleading because, due to the essential presence of a file system as a data structuring mechanism, you'll never get the full capacity of 300GB no matter what file system you use.

In a similar way, you'll never get 2,048kb/s data throughput from a 2Mb/s line, due to the presence of frame markers and error correction/notification bytes that encapsulate the payload data (i.e., the data you consciously send from the transmission side).

Blowfish

It wasn't always the same with 1KB = 1000 bytes, i discovered the other day that i have an old western digital 3GB drive which actually is 3221225472 bytes, i.e. 1KB = 1024 bytes

CyberGhost

Didn't know that either, thanks guys!

astrofool

Blowfish wrote:

It wasn't always the same with 1KB = 1000 bytes, i discovered the other day that i have an old western digital 3GB drive which actually is 3221225472 bytes, i.e. 1KB = 1024 bytes

It's been that way for years. Your drive would have been marked as 3.2gb, you could probably still google the info page for your drive to see.

in fact as you can see here:

http://www.wdc.com/en/products/legacy/Legacy.asp?r=3#physical

"* Western Digital defines a megabyte (MB) as 1,000,000 bytes and a gigabyte (GB) as 1,000,000,000 bytes"

and notice the lack of 3gb model here: http://www.wdc.com/en/products/legacy/legacy.asp?r=3