Jump to content
Sign in to follow this  

Hard Drive Capacity - Standalone

Recommended Posts

I've a standalone hard drive thats supposed to be 300 Gb.


However, it seems that I'm only able to use 279 Gb's.


I cleaned it off i.e. formatted it, and it shows up as Capacity 279. File system NTFS. Allocation Unit Size 4096 bytes.


Any suggestions where the 21 Gb's have gone to?


Any ideas on what the problem may be ??


Can I get back the 300 Gb's ?



Share this post

Link to post
Share on other sites

I think if you took off the OS that it came with and anything else the factory and retailer put on it, you might get closer.


I thought it was common knowledge that all comps or devices that have hard drives are always less than advertised. For example, I recently bought an iPod touch 4G 8GB (yes, I know it's small but I'm not rich) and it only had 6.5GB of usable space. Normal, I thought. My new comp advertises 320GB HDD. On first use, it offered 271 or something like that. I thought that was normal.

Share this post

Link to post
Share on other sites

There are 3 reasons for the discrepancy,


1) Different capacity units used by drive manufactures and the OS.


2) The filesystem takes up space on the drive.


3) Some OS's reserve part of the disk.




"I have a 120 GB hard drive but Windows XP claims it's size is 111.8 GB. What has happened to the other 8.2 GB? "


Hard drive manufacturers calculate hard disk size in 'base 10' notation while Windows does the calculation in 'base 2' (binary) format. Both the manufacturer and Windows are giving you the "correct" number.


1 Gigabyte as defined by a manufacturer is 1,000,000,000,000 Bytes. This makes sense in the metric base 10 sense as we define kilo as 1000, mega as 1,000,000 and giga as 1,000,000,000,000.


Windows, however, calculates the disk size in a base 2 system. Base 2 does not convert into base 10 exactly in most cases but back in the day it was close enough so that a kilobyte was defined as 2^10 or 1024.


2^10 is 1024 is 1 kilobyte

2^20 is 1048576 or 1 megabyte

2^30 is 1073741824 or 1 gigabyte


When the hard disk manufacturer sold you a 120 Gig hard drive, they were selling you 120,000,000,000 bytes. Windows divides this number by what it considers a GB (1073741824) and reports the hard disk size as:


120000000000 (bytes) / 1073741824 (bytes per GB) = 111.8 GB


This accounts for the 'missing' 8.2 GB in the hard disk's size. You still have 120,000,000,000 bytes to use but because of inconsistent definitions of what kilo, mega and giga really represent, there is an inconsistency in the measurement of size.



Share this post

Link to post
Share on other sites

Added to that, is the amount of blocks on the disk that are "bad" and ignored. Some disks have a significant part of the disk unusable due to manufacture error. This is also normal.

Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

  • Create New...