# Re: RAID Sizes (was Re: Why do people in the UK put a u in the word color?)

```Andrei Popescu wrote:
> Willie Wonka <floydstestemail@yahoo.com> wrote:
>
> > Actually - Block sizes are what they are (in binary), because
computers
> > use Binary language to communicate/operate...Many HDD manufacturers
> > just like to *lie* and use a diff integer base (base10)...to make
the
> > HDD look larger. Remember (if you use their base10 game) you lose
> > approximately 99GiB per every TeraByte of space;
> > 1 TB = 10^12 = 1,000,000,000,000 (base10 - decimal)
> > 1 TiB = 2^40 = 1,099,511,627,776 (base2 - binary)

Hi;
though for even posting in this thread - after so many other branches
have grown out sideways into various areas :-)). I didn't realize how
large a post I created either - not to mention the fact; one of my
paragraphs seem to have spontaneously regenerated/duplicated itself.
:-O

> Your calculation is correct, but I would think the other
> 1 TB = 1000 GB which is aprox. 931 GiB. So you loose 69 GiB for every
> TB.

I see you're using the 93.1% rule though...
To me, this is an incorrect way to calculate, since the differences in
sizes, between binary and decimal values, increases as the HDD sizes
increase....i.e.; the larger the HDD, the larger the discrepancy
between base10 and base2 - hence;

Binary Example
1,024
1,048,576
1,073,741,824
1,099,511,627,776

notice the 'column' of numbers (aligned vertically, from the top);
024
048
073
099

The "difference" (between decimal/binary) as sizes increase is _never_
the same *percentage* wise...The binary total is *compounded* as the
sizes increase...(to a degree, and for lack of a better word).

Explained another way (hopefully);
If you bought a 1,000 Byte (1KB) HDD - you'd lose 24 *Bytes*
If you bought a 1,000,000 Byte (1MB) HDD - you'd lose 48 *KiloBytes*
If you bought a 1,000,000,000 Byte (1GB) HDD - you'd lose 73
*MegaBytes*
If you bought a 1,000,000,000,000 Byte (1TB) HDD - you'd lose 99
*GigaBytes*

Pertaining to sizes of HDD -- The more you buy, the more you lose.
The Larger the HDD, the Larger the amount of lost area, in the
conversion.

What you *appear* to be doing (as do many others; likely
unintentionally) is just taking ~93.1% of a given base10 number.

Hence;
1,000,000,000,000 * .931 = 931,000,000,000 = *your* 931 [G]iB *result*
1,000,000,000     * .931 =     931,000,000 = *your* 931 [M]iB *result*
1,000,000         * .931 =         931,000 = *your* 931 [K]iB *result*

But by doing so, you can do this with ANY power of 10 and still arrive
at the *same*percentage* as the sum/total...which is not the case
IMHO....I am open to correction though.

To try and sum up my point;
Everytime you step *up* using a power of 10, you lose MORE when
converting to Binary.

IMHO;
1024 * 1024 = Correct
1024 * 1000 = Incorrect
1000 * 1000 = Incorrect

I think much of the confusion stems from the numeric *starting* point.
Perhaps I'm just Full_of_\$Hit ...and I have been wrong before in my
life :-)

> Here is what I know about HDDs and stuff, someone please correct me
if
> I'm wrong.
>
> Tracks are something else. Physically a HDD is divided into
cylinders,
> heads, tracks and sectors. A track contains more sectors. I would
have
> to draw to explain this nice, but I'm sure you can find that on the
web.

I actually already have nice pictures/diagrams of HDDs, but thank you
;-)
Tracks are clusters of Sectors (of a set size) - AFAIK

In this example, I'll use [Sector=512Bytes] and [Track=4096Bytes = 8
Sectors].
Data (File) that occupies more space than 1 sector (512Bytes), will
fill up those sectors until the Track/Block/Cluster (8 sectors) is
full, ...and a larger File will then  overflow onto the next
Sectors/Track, and so on -- this is merely a consequence of
*contiguous* writing of data.

Fragmentation occurs from Non-contiguous writes to the disk (storage of
data).
Definition;
Contiguous describes two or more objects that are adjacent to
each other. In computing, contiguous data is data that is moved
or stored in a solid uninterrupted block. In general, contiguous
data can be accessed more quickly than data that is stored in
fragments because fewer access operations will be required.
Files are sometimes stored in fragments so that storage space
can be used more efficiently (all the small spaces can be used).

Cylinders are ring-shaped, vertically aligned areas of the HDD - think
of stacking doughnuts or rings; one on top of each other, the only
difference (besides the obvious), is that no 2 stacks of
cylinders/doughnuts/rings are the same physical size...yet they are
stacked vertically (according to the platters). This all starts to get

> The smallest physical unit is the sector which is always 512 B.
> When you format a partition you divide it in allocation units. In
*nix
> they are called blocks, in MS clusters.

Yes, I concur;
but I'd refine it to *a group of sectors, which has a set size*
perhaps.

> Because a sector is 512 B an allocation unit can not be smaller
> then 512 B, and is always a multiple of 512 B.

Agreed

> Andrei

Regards

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