Hard disk size - quoted & actual

G

Guest

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Hi all,

This is something I've often wondered about but never tried to find out
- why is it that when you buy a 400GB drive, hook it up to your
motherboard, you only get say 370GB? This is before it's been formatted
or anything.

I don't normally mind/notice the loss, but I've just built a RAID array,
and it was a bit of a shock that all I ended up with was 1.8TB instead
of 2.0TB.


TIA

--
Grunff
 

peter

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Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

> This is something I've often wondered about but never tried to find out
> - why is it that when you buy a 400GB drive, hook it up to your
> motherboard, you only get say 370GB? This is before it's been formatted
> or anything.
>
> I don't normally mind/notice the loss, but I've just built a RAID array,
> and it was a bit of a shock that all I ended up with was 1.8TB instead
> of 2.0TB.

Capacity is the amount of data that the drive can store,
after formatting. Most disc drive companies, including Seagate,
calculate disc capacity based on the assumption that
1 megabyte = 1000 kilobytes and 1 gigabyte=1000 megabytes.

According to other sources:
1 megabyte = 1024 kilobytes and 1 gigabyte = 1024 megabytes.

Hence the difference.
 
G

Guest

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Peter wrote:

> Capacity is the amount of data that the drive can store,
> after formatting. Most disc drive companies, including Seagate,
> calculate disc capacity based on the assumption that
> 1 megabyte = 1000 kilobytes and 1 gigabyte=1000 megabytes.
>
> According to other sources:
> 1 megabyte = 1024 kilobytes and 1 gigabyte = 1024 megabytes.
>
> Hence the difference.


But that doesn't quite account for the discrepancy. For example, my
drives are these:

<http://uk.insight.com/apps/productpresentation/index.php?product_id=HTGA03UOS>

They are quoted as 400GB drives, and yet my system sees them as 372GB
drives. The 1000/1024 difference isn't big enough - 372 * 1.024 = 381GB.


Any other explanations?

--
Grunff
 
G

Guest

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Grunff wrote:

> Peter wrote:
>
>> Capacity is the amount of data that the drive can store,
>> after formatting. Most disc drive companies, including Seagate,
>> calculate disc capacity based on the assumption that
>> 1 megabyte = 1000 kilobytes and 1 gigabyte=1000 megabytes.
>>
>> According to other sources:
>> 1 megabyte = 1024 kilobytes and 1 gigabyte = 1024 megabytes.
>>
>> Hence the difference.
>
>
> But that doesn't quite account for the discrepancy. For example, my
> drives are these:
>
>
<http://uk.insight.com/apps/productpresentation/index.php?product_id=HTGA03UOS>
>
> They are quoted as 400GB drives, and yet my system sees them as 372GB
> drives. The 1000/1024 difference isn't big enough - 372 * 1.024 = 381GB.
>
>
> Any other explanations?

The drive manufacturer reports unformatted capacity--since they don't know
what file system you're going to be using they can't report anything else
and have it mean anything. When the drive is formatted a certain amount of
space is taken up by the structures the operating system uses to keep track
of which file is in which sector and provide services such as journalling.
The capacity that the OS reports is what's left after that has been done.

To take one well known example, the common 3.5" HD diskette has an
unformatted capacity of 2 meg, but formatted under DOS its capacity is
reduced to 1.44 meg.


--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
 

peter

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> Peter wrote:
>
> > Capacity is the amount of data that the drive can store,
> > after formatting. Most disc drive companies, including Seagate,
> > calculate disc capacity based on the assumption that
> > 1 megabyte = 1000 kilobytes and 1 gigabyte=1000 megabytes.
> >
> > According to other sources:
> > 1 megabyte = 1024 kilobytes and 1 gigabyte = 1024 megabytes.
> >
> > Hence the difference.
>
>
> But that doesn't quite account for the discrepancy. For example, my
> drives are these:
>
>
<http://uk.insight.com/apps/productpresentation/index.php?product_id=HTGA03U
OS>
>
> They are quoted as 400GB drives, and yet my system sees them as 372GB
> drives. The 1000/1024 difference isn't big enough - 372 * 1.024 = 381GB.
>
>
> Any other explanations?

No, it is the same explanation:
kBytes to KBytes conversion takes 1.024
mBytes to MBytes conversion takes another 1.024
gBytes to GBytes conversion takes yet another 1.024

Now calculate:
372*1.024*1.024*1.024=399.432
assume you had not exactly 372 but 372.499999
372.499999*1.024*1.024*1.024=399.969
I think that is close enough to 400gB, ooops, they say 400GB ;-)
 
G

Guest

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Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

It is 400GB / 1.024^3 = 370GiB.

"Grunff" <grunff@ixxa.com> wrote in message
news:1114636289.17707.0@nnrp-t71-02.news.clara.net...
>
> But that doesn't quite account for the discrepancy. For example, my
> drives are these:
>
>
<http://uk.insight.com/apps/productpresentation/index.php?product_id=HTGA03UO
S>
>
> They are quoted as 400GB drives, and yet my system sees them as 372GB
> drives. The 1000/1024 difference isn't big enough - 372 * 1.024 = 381GB.
>
 
G

Guest

Guest
Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

"Grunff" <grunff@ixxa.com> wrote in message news:1114636289.17707.0@nnrp-t71-02.news.clara.net
> Peter wrote:
>
> > Capacity is the amount of data that the drive can store,
> > after formatting. Most disc drive companies, including Seagate,
> > calculate disc capacity based on the assumption that

> > 1 megabyte = 1000 kilobytes and 1 gigabyte = 1000 megabytes.

and 1 kilobyte = 1000 bytes.

> >
> > According to other sources:

> > 1 megabyte = 1024 kilobytes and 1 gigabyte = 1024 megabytes.

and 1 kilobyte = 1024 bytes.

> >
> > Hence the difference.
>
>
> But that doesn't quite account for the discrepancy.

Yes it does.

> For example, my drives are these:
>
> <http://uk.insight.com/apps/productpresentation/index.php?product_id=HTGA03UOS>
>
> They are quoted as 400GB drives, and yet my system sees them as 372GB
> drives. The 1000/1024 difference isn't big enough - 372 * 1.024 = 381GB.

372*1024B*1024B*1024B = 399.432GB = ~400GB
373GiB -> 400.5 GB, The 372 was likely rounded.


>
>
> Any other explanations?

Nope.
 
G

Guest

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J. Clarke wrote:

> The drive manufacturer reports unformatted capacity--since they don't know
> what file system you're going to be using they can't report anything else
> and have it mean anything. When the drive is formatted a certain amount of
> space is taken up by the structures the operating system uses to keep track
> of which file is in which sector and provide services such as journalling.
> The capacity that the OS reports is what's left after that has been done.


Sorry, perhaps I wasn't clear - this is the disk size reported by the
motherboard, before the disks have been formatted.


--
Grunff
 
G

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Peter wrote:

> Now calculate:
> 372*1.024*1.024*1.024=399.432
> assume you had not exactly 372 but 372.499999
> 372.499999*1.024*1.024*1.024=399.969
> I think that is close enough to 400gB, ooops, they say 400GB ;-)


Ahh...that makes sense. Many thanks.


--
Grunff
 
G

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Peter <peterfoxghost@yahoo.ca> wrote in message
news:auRbe.7627$BW6.776133@news20.bellglobal.com...

>> This is something I've often wondered about but never
>> tried to find out - why is it that when you buy a 400GB
>> drive, hook it up to your motherboard, you only get say
>> 370GB? This is before it's been formatted or anything.

>> I don't normally mind/notice the loss, but I've just
>> built a RAID array, and it was a bit of a shock that
>> all I ended up with was 1.8TB instead of 2.0TB.

> Capacity is the amount of data that the drive can store,
> after formatting. Most disc drive companies, including
> Seagate, calculate disc capacity based on the assumption that
> 1 megabyte = 1000 kilobytes and 1 gigabyte=1000 megabytes.

It isnt an assumption, thats the standard SI unit.

And all hard drive manufacturers state the drive size that way.

> According to other sources:

Who get it wrong. There is nothing intrinsically binary about
hard drive capacity. Thats only seen with ram and rom.

> 1 megabyte = 1024 kilobytes and 1 gigabyte = 1024 megabytes.

> Hence the difference.

Indeed.
 
G

Guest

Guest
Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

> Who get it wrong. There is nothing intrinsically binary about
> hard drive capacity. Thats only seen with ram and rom.

Well, the basis of the measurement of a bit (Binary digIT) is of course
binary. A byte = 8 bits, and traditionally, these measurements are
portrayed in powers of two. So, it makes sense to represent bits or
bytes in powers of two. Of course, decimal arithmatic is more natural
for most people to compute (and it's probably easier to market products
with nice, round numbers), so there are tradeoffs.

//Kevin
 
G

Guest

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Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

Grunff <grunff@ixxa.com> wrote in message
news:1114636289.17707.0@nnrp-t71-02.news.clara.net...
> Peter wrote

>> Capacity is the amount of data that the drive can store,
>> after formatting. Most disc drive companies, including Seagate, calculate
>> disc capacity based on the assumption that
>> 1 megabyte = 1000 kilobytes and 1 gigabyte=1000 megabytes.

>> According to other sources:
>> 1 megabyte = 1024 kilobytes and 1 gigabyte = 1024 megabytes.

>> Hence the difference.

> But that doesn't quite account for the discrepancy.

Yes, the rest is 'lost' to the directory structures etc after formatting.

> For example, my drives are these:

> <http://uk.insight.com/apps/productpresentation/index.php?product_id=HTGA03UOS>

> They are quoted as 400GB drives, and yet my system sees them as 372GB drives.
> The 1000/1024 difference isn't big enough - 372 * 1.024 = 381GB.

> Any other explanations?

The directory structures etc, and in your case with RAID,
what gets used to keep the RAID info on the drives.
 
G

Guest

Guest
Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

"Rod Speed" <rod_speed@yahoo.com> wrote in message news:3dae7jF6qhor1U1@individual.net
> Grunff <grunff@ixxa.com> wrote in message
> news:1114636289.17707.0@nnrp-t71-02.news.clara.net...
> > Peter wrote
>
> > > Capacity is the amount of data that the drive can store,
> > > after formatting. Most disc drive companies, including Seagate, calculate
> > > disc capacity based on the assumption that
> > > 1 megabyte = 1000 kilobytes and 1 gigabyte=1000 megabytes.
>
> > > According to other sources:
> > > 1 megabyte = 1024 kilobytes and 1 gigabyte = 1024 megabytes.
>
> > > Hence the difference.
>
> > But that doesn't quite account for the discrepancy.
>
> Yes, the rest is 'lost' to the directory structures etc after formatting.

Clueless.

>
> > For example, my drives are these:
>
> > <http://uk.insight.com/apps/productpresentation/index.php?product_id=HTGA03UOS>
>
> > They are quoted as 400GB drives, and yet my system sees them as 372GB drives.
> > The 1000/1024 difference isn't big enough - 372 * 1.024 = 381GB.
>
> > Any other explanations?
>
> The directory structures etc, and in your case with RAID,
> what gets used to keep the RAID info on the drives.

Utter nonsense.
 
G

Guest

Guest
Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

Grunff wrote:

>Hi all,
>
>This is something I've often wondered about but never tried to find out
>- why is it that when you buy a 400GB drive, hook it up to your
>motherboard, you only get say 370GB? This is before it's been formatted
>or anything.

Hi all, This is something I've often wondered about but never tried to
find out - why is it that cretins are always coming along asking
questions like this, in the apparent belief that they are the first
person ever to post the question on USENET? Do they think they're
that unique? Have they never heard of doing a google search?
 
G

Guest

Guest
Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

Folkert Rienstra wrote:

> 372*1024B*1024B*1024B = 399.432GB = ~400GB
> 373GiB -> 400.5 GB, The 372 was likely rounded.

Yup, got it now, thanks.


--
Grunff
 
G

Guest

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Kevin Buffardi <kevin.buffardi@email.com> wrote in message
news:427044da$0$79459$14726298@news.sunsite.dk...

>> Who get it wrong. There is nothing intrinsically binary about
>> hard drive capacity. Thats only seen with ram and rom.

> Well, the basis of the measurement of a bit (Binary digIT) is of course
> binary.

Thats not what base 2 means in this situation.

> A byte = 8 bits, and traditionally, these measurements are portrayed in powers
> of two.

Thats just plain wrong. The 1.44MB floppy
is in fact a weird binary/decimal hybrid.

> So, it makes sense to represent bits or bytes in powers of two.

Only when the total bytes are binary organised.
They aint with a hard drive or the cpu speed either.

> Of course, decimal arithmatic is more natural for most people to compute

And is the SI standard.

> (and it's probably easier to market products with nice, round numbers), so
> there are tradeoffs.

Its much more complicated than that, as the 1.44MB floppy shows.
 
G

Guest

Guest
Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

>>A byte = 8 bits, and traditionally, these measurements are portrayed in powers
>>of two.
>
> Thats just plain wrong.

I suggest you read "The Principles of Computer Hardware" (Alan
Clements). It lays out the foundation of computer hardware in decimal
arithmatic. The acronym "bit" itself comes from Binary digIT, 0 or 1.
It's the origin of terminology, so yes, *traditionally*, bits are
represented in powers of two.

Note the word "traditionally." Not "always," but "traditionally."
 
G

Guest

Guest
Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

> It lays out the foundation of computer hardware in decimal
> arithmatic.

Misspoken: "Binary arithmetic."
 
G

Guest

Guest
Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

chrisv wrote:

> Hi all, This is something I've often wondered about but never tried to
> find out - why is it that cretins are always coming along asking
> questions like this, in the apparent belief that they are the first
> person ever to post the question on USENET? Do they think they're
> that unique? Have they never heard of doing a google search?


While I'd normally ignore idiotic responses such as this, since this is
my first post to the group, I'll respond.

I did google, extensively, this group (including its FAQ), other groups,
and the web. I found lots of questions, but no answers that satisfied my
curiosity.

I found lots of answers referring to file system overhead etc., as
posted by several people in this thread - but my question is about
non-formatted drives.

I now understand the reason, and also understand the mistake I was
making (1024 not 1024^3), thanks to some very helpful answers.

There will always be some level of repetition on Usenet - learn to live
with it.


--
Grunff
 
G

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Kevin Buffardi <kevin.buffardi@email.com> wrote in message
news:42706469$0$79454$14726298@news.sunsite.dk...

>>> A byte = 8 bits, and traditionally, these measurements are portrayed in
>>> powers of two.

>> Thats just plain wrong.

Most obviously with hard drives. Also with telecoms.

> I suggest you read "The Principles of Computer Hardware" (Alan Clements).

Dont need to, I know that is just plain wrong.

And I've been doing it since before Clements has too.

> It lays out the foundation of computer hardware in decimal arithmatic.

Irrelevant to that particular pig ignorant claim.

> The acronym "bit" itself comes from Binary digIT, 0 or 1.

I didnt even comment on that.

> It's the origin of terminology, so yes, *traditionally*, bits are represented
> in powers of two.

> Note the word "traditionally." Not "always," but "traditionally."

Its still just plain wrong. Its only really been true of memory. And
that is because it does have an intrinsically binary ORGANISATION.
 
G

Guest

Guest
Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

>>The acronym "bit" itself comes from Binary digIT, 0 or 1.
>
>
> I didnt even comment on that.

Well that was my comment. Then you said it was wrong.

> Its still just plain wrong. Its only really been true of memory. And
> that is because it does have an intrinsically binary ORGANISATION.

I'm sorry if my first post was misleading, but I believe you are
misinterpreting it from my intentions. I never mentioned memory or
storage. I am talking about the origin of the terms bit and byte.
Those origins predate the use of the magnetic, non-volatile storage we
use today.

Both Peter and Folkert showed how binary arithmetic demonstrates the
difference between advertised size, and size represented in binary.

Your explanation of space taken by directory structures and such would
hold some credence if the disk was already formatted. However, Grunff
specified that the disk in question was unformatted and reported as
370GB by the motherboard (presumably in CMOS/BIOS).

//Kevin
 
G

Guest

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Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

Kevin Buffardi wrote:
> I'm sorry if my first post was misleading, but I believe you are
> misinterpreting it from my intentions.

Yes, upon reinspection I can see where I left too much of your quoted
text in, implying that I was referring specifically to storage capacity
when I was not. My apologies.

//Kevin
 

nick

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Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

On Wed, 27 Apr 2005 21:05:30 -0500, Kevin Buffardi
<kevin.buffardi@email.com> wrote:

>> Who get it wrong. There is nothing intrinsically binary about
>> hard drive capacity. Thats only seen with ram and rom.
>
>Well, the basis of the measurement of a bit (Binary digIT) is of course
>binary. A byte = 8 bits,

http://en.wikipedia.org/wiki/Byte

The word "byte" has several meanings, all closely related:

1. A contiguous sequence of a fixed number of bits. On modern
computers, an eight-bit byte or octet is by far the most common. This
was not always the case. Certain older models have used six-, seven-,
or nine-bit bytes - for instance on the 36-bit architecture of the
PDP-10. Another example of a non eight-bit sequence is the 12-bit slab
of the NCR-315. A byte is always atomic on the system, meaning that it
is the smallest addressable unit. An eight-bit byte can hold 256
possible values (28 = 256) -- enough to store an unsigned integer
ranging from 0 to 255, a signed integer from -128 to 127, or a
character of a seven-bit (such as ASCII) or eight-bit character
encoding.


Nick
 
G

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Nick wrote:
> 1. A contiguous sequence of a fixed number of bits. On modern
> computers, an eight-bit byte or octet is by far the most common. This
> was not always the case. Certain older models have used six-, seven-,
> or nine-bit bytes - for instance on the 36-bit architecture of the
> PDP-10.

While it's true that a byte doesn't always have to be 8-bits, it's
notable that these cases are rare. Even as the beloved Wikipedia says,
"eight-bit byte [...] is by far the most common." But, no excuses for
me... I should have said, "A byte *typically* = 8 bits."

Another thing to point out that is even more relavent to the thread:
http://en.wikipedia.org/wiki/Kilobyte

As shown here, yes Rod is correct that 1KB = 1000 bytes in International
System of Units standards. HOWEVER, "1,024 [...] is used to express
memory capacity *and by most software to express storage capacity.*
This was obviously the case for Grunff's mobo report of the hard drive
capacity.

//Kevin
 
G

Guest

Guest
Archived from groups: comp.sys.ibm.pc.hardware.storage (More info?)

Previously Grunff <grunff@ixxa.com> wrote:
> Hi all,

> This is something I've often wondered about but never tried to find out
> - why is it that when you buy a 400GB drive, hook it up to your
> motherboard, you only get say 370GB? This is before it's been formatted
> or anything.

HDD manufactueres sell you n units of storage. The legal units are
prefixed by SI prefixes, i.e. multiples of 1000. Ram is sold in
number of address lines, which results in powers of two. Thes units
are illegal, but since you cannot have a 19MB chip or the like, these
are not considerd units of measurement but instead something like
size-classes, like a 2 family house or a 4 person car. However since
HDDs can have almost any size, the manufacturers are required by
law almost anywhere to use the correct SI prefixes.

> I don't normally mind/notice the loss, but I've just built a RAID array,
> and it was a bit of a shock that all I ended up with was 1.8TB instead
> of 2.0TB.

You have 2TB. You also habe 1.8TiB. Ti is not a legal SI prefix,
but a IEC standard exists. Look here:

http://physics.nist.gov/cuu/Units/binary.html

If somebody shows 2TB as 1.8TB they are in violation of the laws
on units and measurements in allmost all countries. Not that
anybody seems to care.

Arno
 

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