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Stupid Question- Hard Disk Drives and Space on them

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Stupid Question- Hard Disk Drives and Space on them

Old 05-28-06, 12:23 PM
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Stupid Question- Hard Disk Drives and Space on them

Guess what? this isn't the question you're expecting- but it is related.

For years- due to the way that HDs are formatted, they've shown less space than they're advertised as having. I remember buying a 40MB drive maybe 15 years ago and being upset that I only got 37 megs. And on any given tech board, there's always a newbie asking why their 250 gig drive is smaller than they expected. It's always answerd the same way, because the formatting of the computer is slightly different, so formatted size may vary.

So why the hell don't manufacturers just throw in a bit more pre-formatted space? They know EXACTLY how much extra is necessary to get to the advertised number, so why not just throw in 285gigs, advertise it as a 250 gig drive, so when it's formatted, you actually GET 250 gigs?

I can't POSSIBLY be the only person to think up this idea, can I?

-jason
Old 05-28-06, 03:42 PM
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It's not a question of the formating but of the way a MB is being represented. The HD manufacturers uses a MB using base 10 while most operating systems use base 2. (so 10^6 vs 2^20). I think strictly speaking, they really are providing the space as advertised, but the number system has created confusion.

There is another unit called a "Mebibyte" (MiB) that's supposed to help break the confusion by only using base 2 and then leave MB using base 10 only. (I've never seen anything advertised using MiB though).

If using Windows XP, your drive properties show both the GB (which should really be GiB) using base 2 and then the explicit number of bytes associated with it.

Last edited by UWSarge; 05-28-06 at 03:47 PM.
Old 05-28-06, 06:15 PM
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Originally Posted by UWSarge
The HD manufacturers uses a MB using base 10 while most operating systems use base 2. (so 10^6 vs 2^20). I think strictly speaking, they really are providing the space as advertised, but the number system has created confusion.
But when it comes down to it, the HD manufacturers are using a system that is ONLY useful to them, and approx. 90% of their users are using a different system, so why stick to the old one?

If they made a 285 gig drive, like in my example, and called it 250, windows users would be happy because they get what they bought, and anyone using an OS that works on base 10 (whatever that might be- unix?) will be very happy because they think they're getting one over on the manufacturers when they get 285. Everyone wins.

Maybe I'll just have to subcontract out with an HD manufacturer and private-brand my own drives- call them "TrueSize" Hard drives or something silly like that...

-jason
Old 05-29-06, 10:29 AM
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Because this way, they can sell a "250" GB HD, and only really have to manufacture the equivalent of, say, a 235 GB HD (using the base 2 notation). If it's working for you, why raise your costs by adding more material? All comes down to that lovely profit margin...
Old 05-31-06, 08:57 AM
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I can think of two reasons why your suggested idea wouldn't be meaningful.

1. Everyone's used to 250gb meaning a certain amount of real disk space, say around 230gb. If I was to start selling 270gb disks and calling them 250gb so everyone got a real 250gb then I'd have to spend more money on making the disk than the guy next door who's only selling 250/230gb. As such I'd charge more than he does. But we'd both advertise the disks as being 250gb so no one buys my disks and I go bankrupt.

2. The second problem is to do with the disk space itself. Suppose I've actually got 250gb available on my disk. How many 1gb files can I put there? Well it sounds like the answer should be 250. But, of course, it isn't, as I put files on there the system will create directory files, pointer etc that will themselves use up space. Plus the decive is split into sectors, clusters and blocks. The file system will determine the smallest available unit. The smaller the units you set it for the more disk space will be taken off the top from the "real" disk space before I see the actual disk space. So to resolve that we could set the "minimum" unit at a large number thereby reducing the formatting space needed. Suppose (and this is an example nothing would really be this big) I set the minimum block size at 1.5 gb. I'd need very little file pointer space with so few blocks but then the minimum size a file would take up would be 1.5 gb. Anything smaller from 1 byte to 1.5gb is just forced to use the full minimum block.

So with 1gb files I'd only get around 170 files on a true 250gb available space.

You can see this affect if you look in Windows Explorer where it will give both the true file size, in bytes and the disk space its using (in bytes). The difference is the wasted amount owing to block sizes.

The point being that whatever you do you're never going to really get 250 1gb files on a 250gb disk. There's always going to be wasted space, there's always going to be space allocated for formatting and file pointers.

So why change things. Don't worry about 250gb as a "hard" number, think of it, instead, as a proportional size compared to other disks.
Old 05-31-06, 09:29 AM
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Originally Posted by davidoflondon
1. Everyone's used to 250gb meaning a certain amount of real disk space, say around 230gb.
I'd say a LOT of people are, but not everyone. go to any tech board, and I'll bet even this one- you'll have no problem finding a post asking why their newly formatted drive is showing less space than they bought. I've even noticed it in the comments on Newegg- and you can't tell me those people are all novices.

Originally Posted by davidoflondon
If I was to start selling 270gb disks and calling them 250gb so everyone got a real 250gb then I'd have to spend more money on making the disk than the guy next door who's only selling 250/230gb. As such I'd charge more than he does. But we'd both advertise the disks as being 250gb so no one buys my disks and I go bankrupt.
That's where you fail to see my brilliance. My advertising campaign will focus on "truly getting what you buy". It'll have some sad guy formatting a computer and getting only 235 gigs, then a happy guy buying one of my 250 gig drives, formatting it and having windows say "250 gigs" and he'll be happy, sun will shine, and birds will sing. People won't mind paying a premium price for my drives because they'll be getting what they buy. Too bad John Houseman is dead- he'd make a great spokesman.

And honestly, the cost of putting on an extra 25 or so gigs nowadays is so trivial that the premium price wouldn't have to amount to more than a 5% increase, I think.

Originally Posted by davidoflondon
2. The second problem is to do with the disk space itself. Suppose I've actually got 250gb available on my disk. How many 1gb files can I put there? Well it sounds like the answer should be 250. But, of course, it isn't, as I put files on there the system will create directory files, pointer etc that will themselves use up space. Plus the decive is split into sectors, clusters and blocks. The file system will determine the smallest available unit. The smaller the units you set it for the more disk space will be taken off the top from the "real" disk space before I see the actual disk space. So to resolve that we could set the "minimum" unit at a large number thereby reducing the formatting space needed. Suppose (and this is an example nothing would really be this big) I set the minimum block size at 1.5 gb. I'd need very little file pointer space with so few blocks but then the minimum size a file would take up would be 1.5 gb. Anything smaller from 1 byte to 1.5gb is just forced to use the full minimum block.
Ok, you lost me there about halfway through, but it seems like it's a universal problem with any size, so it's not my concern.

(of course this is all my pipe dream anyway- you think I have capital to actually do this???)

-jason

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