[geeks] Advice on buying a new Mac

[John Francini]

On 14 Nov 2006, at 10:34, Jonathan C. Patschke wrote:

> On Mon, 13 Nov 2006, Patrick Giagnocavo wrote:
>
>> No, if you mean "will it pull data off the disk as fast".  Reason is
>> twofold:
>
> <snip>
>
>> 2. the physical drive platter is smaller, thus, even though  
>> rotating at
>> the same speed, the swept area (whatever the technical term is) is  
>> less
>> than a larger platter.
>
> It takes more time to traverse a smaller distance?
>

No.

> As far as I know, most drives still use a concentric sector layout, so
> the number of sectors per angle is a constant across all tracks.  The
> density of the inner tracks is bound by the coercivity of the medium,
> and the density of the outer tracks is limited by the rotational speed
> of the medium.  Packing in the absolute maximum amount (through a  
> single
> spiraling track of sectors like CDs use) of storage would complicate
> drive electronics significantly.

Actually, hard drives went away from a strict concentric sector  
layout years ago. To pack the most sectors in a given space, the  
surface of the hard drive is divided into a number of concentric  
'zones'.  All of the tracks in a given zone have the same number of  
sectors.  Each zone, however, has a different number of sectors  
depending on where it's located on the disk: outer zones have far  
more sectors than inner zones.  This zoned approach keeps the number  
of sectors per unit area of surface within a narrow range that  
maximizes data storage.

So, there IS more data "under the head" of a disk on the outer tracks  
than on the inner tracks, simply by dint of the zoned sector layout.

John