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ianhnz
08-03-2009, 08:14 PM
I purchased a preloved Maxtor 40 GB hard drive off Trade Me. It is formatted as NTFS. can someone please tell me why Windows says it's 38.2 GB's and not 40? Thanks, Ian.

Blam
08-03-2009, 08:30 PM
Basically, in simple terms,

Your operating system usually sees a binary representation of hard drive space whilst a hard drive manufacturer uses the decimal representation.

i.e Decimal Representation of 1kb=1000bytes

Binary Representation of 1kib=1024bytes

The slight difference adds up to a bit more when you get to bigger stuff, such as 40-1000gb HDs

Personally I think its just a scam from HD manufacturers to make their drives look bigger. But the whole picture is incredibly complicating...

HTH
Blam

Speedy Gonzales
08-03-2009, 08:41 PM
And you'll never use all of a hdd. No matter how big it is

ianhnz
08-03-2009, 08:51 PM
Ok, thanks. So it's more of a math program than am issue with the drive? Wasn't sure if it was something to do with a "mirror file" after formating. I think that "quick' formating produces a mirror image, of some sort.:thumbs:

somebody
08-03-2009, 08:57 PM
It's a marketing problem really - hard drive manufacturers making their drives sound bigger than they actually are, by using a different measurement.

Blam
08-03-2009, 09:06 PM
Ok, thanks. So it's more of a math program than am issue with the drive? Wasn't sure if it was something to do with a "mirror file" after formating. I think that "quick' formating produces a mirror image, of some sort.:thumbs:

What do you mean by "Mirror image"?


It's a marketing problem really - hard drive manufacturers making their drives sound bigger than they actually are, by using a different measurement.

Thats arguable actually-If you use the decimal system you know exactly how many bytes your HD will be able to hold, while with a binary system you will have to calculate how many bytes your HD can hold....

ianhnz
08-03-2009, 09:10 PM
Thinking back to my dos days, if you did a 'quick' formate you could run 'unformat' to restore. Don't know if Windows does that too.:confused:

Blam
08-03-2009, 09:15 PM
Would be good if it could-but sadly it can't:(

But-IIRC a quick format only deletes the files in the partitions, so if you don't use the space, you can probably recovery everything to its original state using a file recovery program.

jwil1
08-03-2009, 09:16 PM
A bit OT, but anyway... There is a way to calculate how much space you actually get, based on the marketed capacity:

Marketed capacity / 1.024 / 1.024 / 1.024 = Actual Usable Capacity

Blam
08-03-2009, 09:20 PM
I forgot where-but I read somewhere that the easiest way to do it, without a calculator is 0.93 x capacity of HDD from manufacturer for Hds less than a terabyte and 0.91x capacity of Hds 1 terabyte and beyond.

Its usually quite accurate

ianhnz
08-03-2009, 09:23 PM
That works out at 37.2 GB, so about right. Thanks.:thumbs:

Erayd
09-03-2009, 12:45 AM
Remember also that the filesystem itself takes up some space - how much depends on which filesystem you're using, how much you are storing, which cluster size you're using and how fragmented the drive is. If you're using a journalling fs, you'll also need to take the journal into account.

ianhnz
09-03-2009, 07:38 AM
Thanks guys...:thanks:thanks

Rob99
09-03-2009, 10:23 AM
Personally I think its just a scam from HD manufacturers to make their drives look bigger. But the whole picture is incredibly complicating...
Its called rounding.

A 2L car engine may be slightly more or less than 2000cc.

91 octane petrol will be a minium of 91, but may be slightly more.

Nothing funny going on here.

Erayd
09-03-2009, 11:45 AM
Its called rounding. <snip> Nothing funny going on here.

Actually, it's not just rounding - this has been a major bone of contention with HDD manufacturers for quite some time. They're the only players in the computer industry who use decimal (1000) units (and yes, they do it to make their drives appear larger). Everyone else uses base-two (1024) units.

Scouse
09-03-2009, 11:57 AM
Hi Rob.
re: A 2L car engine may be slightly more or less than 2000cc.

Many years ago in the UK road licence fees depended on the engine capcity. When I was riding small motorbikes, I was told by my local service agent that a 197 cc engine was classified and charged as a 200 cc so that if it had to be rebored (as was the fashion occasionally in those days after ring problems) it would still come home under the 200 cc level. True or false I never found out but I always found that the actual was smaller than the quoted - possibly for that reason. :rolleyes:

ianhnz
09-03-2009, 12:24 PM
Thanks again. Some very interesting comments.

hueybot3000
09-03-2009, 03:49 PM
Yeah engines always seem smaller, like mine is 3800cc but is actually 3788 or something

ianhnz
09-03-2009, 03:55 PM
I know what you mean. Mines a 2,255cc but it says 2.3 litre. Close enough:clap

hueybot3000
09-03-2009, 03:57 PM
Dont ya just feel ripped off though?