Solved

XP Showing HardDrive Size Smaller Than Physical Size - Why?

Posted on 2007-03-18
4
527 Views
Last Modified: 2008-01-09
Hi all -
Scenario is this - XP Pro XP2 w/ updates. Three Western Digital harddrives - 1 x 120g, 2 x 320g.
XP shows the 120 as 111.79 and the 320's are shown as 298.09 ....
I've just bought the 2nd 320 as a recovery disk to image the first 320 to - and it tells me it's too small!
So .... XP is telling me 298.09 .... does it just 'report' it that way for some damn reason OR are my 320's acutally physically smaller than what's on the label and if so does anyone know why?

(Accept my appologies in advance if this type of question has been covered before but I could not find a similar question in my searches.)

Thanks very much in advance .....

(anyone want a week old 320? Grrrrrrrr!!)



0
Comment
Question by:DAQLD
  • 2
4 Comments
 
LVL 12

Accepted Solution

by:
ibu1 earned 100 total points
ID: 18742936
here's the explanation:

Most operating systems define a hard disk drives capacity using binary or base-2 mathematics. This translates to 1 gigabyte (GB) equal to 1,073,741,824 bytes. This is the correct value when using binary or base-2 mathematics.

However, hard disk drive manufacturers define drive sizes using base-10 mathematics, in which 1 GB is equal to 1,000,000,000 bytes (rather than the 1,073,741,824 bytes, as listed above).

This discrepancy in reporting drive sizes (base-2 vs. base-10) may lead you to believe that you have a hard disk drive of less than expected capacity if you compare the figure reported by the operating system with the figure reported by your documentation, although the actual hard drive size is identical. Microsoft® Windows® simply counts the size differently, and will report a different, slightly smaller, figure.


so basically the hard drive manufacturers and the OS programmers used different bases that led to the discrepancy.
hope this helps!!
0
 
LVL 70

Assisted Solution

by:KCTS
KCTS earned 75 total points
ID: 18742959
... and in addition to ibu1's very accurate explanation of how the binary calculations lead to dicrepancies, there is the additional factor that manufacturers also quote the 'non-formatted' capacity. Once the disk is actually formatted some capacity if lost in the process as it it used to hond disk info, directory structure etc.. This and the binary maths issue resuts in typcal sizes being in the region of 10% lower than the manufacture's published capacity.
0
 

Author Comment

by:DAQLD
ID: 18743019
Gents, thank you both.
My lamen response? That sucks.
Especially the "This and the binary maths issue resuts in typcal sizes being in the region of 10% lower than the manufacture's published capacity" part ... makes you wonder what other things we don't know.
If I find out tomorrow that my new C2D is only as good as first Celeron 400, I'll peak! :0

I'm at a bit of a loss as to my my '320' image won't fit on my empty '320' disk but I guess that a whole other set of points .... I guess I can look forward to spending another $200+ tomorrow on a 500Gig that's only going to be around 460 by the sounds of things.
Thanks again for your explanations and solving this little mystery for me - I'll split between you both.
0
 

Author Comment

by:DAQLD
ID: 18754850
Just as a footnote - my 400 gig drive clocks in at 372.61gig.
0

Featured Post

Free Tool: ZipGrep

ZipGrep is a utility that can list and search zip (.war, .ear, .jar, etc) archives for text patterns, without the need to extract the archive's contents.

One of a set of tools we're offering as a way to say thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
Raid 6 or Raid 10? 19 284
Hot Spare Testing on Non-HotSwap server 6 73
Video disks such as Seagate Pipeline in servers, PCs or NAS boxes. 5 48
Server backups 5 61
As hardware bugs go, this is a strange one! I upgraded a laptop in December 2011 with a 512GB Crucial m4 2.5-inch/9.5mm SATA Solid State Drive (SSD), Crucial part number CT512M4SSD2: http://www.crucial.com/store/partspecs.aspx?IMODULE=CT512M4SSD2 …
For both online and offline retail, the cross-channel business is the most recent pattern in the B2C trade space.
This video Micro Tutorial explains how to clone a hard drive using a commercial software product for Windows systems called Casper from Future Systems Solutions (FSS). Cloning makes an exact, complete copy of one hard disk drive (HDD) onto another d…
Two types of users will appreciate AOMEI Backupper Pro: 1 - Those with PCIe drives (and haven't found cloning software that works on them). 2 - Those who want a fast clone of their boot drive (no re-boots needed) and it can clone your drive wh…

821 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question