still havin probs :)

[Jeffrey Watts]

On 22 Oct 2000, Randy Reames wrote:

> Doesn't the outer edge of the disk spin slower then the inside, and
> have a larger area for the arm to store and retrieve data? Wouldn't it
> be the slower part of the disk?

The outer edge spins faster than the inside, in terms of meters per
second.  It used to be that any given track (ring) of a disk had the same
amount of sectors, so the inside track and the outside track contained the
same amount of data, so the data was read at the same rate regardless of
the position of the head.

Modern hard disks have long since stopped wasting space, and the outer
tracks contain many, many more sectors than the inside tracks.  Since the
platter rotates at a constant speed, more sectors pass under the heads on
the outer tracks every second than the inner tracks.

Now, generally one wants the most heavily read and written to area of the
disk to be on the outside, to take advantage of this performance.  There
are other things to consider, such as seek time (you don't want two
heavily used areas on the disk to be far apart, as head seek is the
bottleneck), but that's not necessarily a concern since many modern hard
drive microcontrollers (the ones on-disk) and hard drive controllers know
the disk geometry and organize writes to more efficiently use the head's
motion (similar to Out-Of-Order execution on processors).

There's a lot more to it, but for most folks outside is best.

> Do partitions work from the inside out? (Sda1 = inside, sda7 =
> outside)

Yes.  All disk media in computers starts at the middle and goes outward.  
That's why when you look at a CD you'll see that most of them don't go all
the way out to the far edge of the disc.

J.

o-----------------------------------o
| Jeffrey Watts                     |
| watts at jayhawks.net         o-------------------------------------------o
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