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

```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)

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.

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.

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. If you make the allocation
units to big you lose space (slack), if you make them too small you
might hit filesystem limitations, because the address space is limited.
This is why MS had to switch from FAT16 to FAT32.

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

Andrei
--
If you can't explain it simply, you don't understand it well enough.
(Albert Einstein)

```