[KLUG Members] re: Revolutionary CD Drives & Rotations Per

[Mike Williams]

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>From: Adam Williams <adam@morrison-ind.com>
>To: members@kalamazoolinux.org
>Date: 18 Jul 2003 14:55:24 -0400
>Reply-To: members@kalamazoolinux.org
>
>  
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>>> Hard drives have always been Constant Angular Velocity.  CAV runs the 
>>> motor at a constant speed, but the media will be going over the head 
>>> faster on the outside than the inside.  This makes less efficient use of 
>>> the storage capability since you will have small sectors on the inner 
>>> tracks and larger ones on the outside.  
>>    
>>
>
>Actually the newer fixed disk drives use variable sector/block (called
>Zone Bit Recording, or ZBR) sizes to make more efficient use of that
>outer space,  it is one of the reasons you've seen an explosion in disk
>capacity - not so much an increase in density (although that has
>happened too) but an increase in the efficient use of the platter's
>surface.
>
>See ftp://ftp.kalamazoolinux.org/pub/pdf/DiskMan1.pdf for some diagrams.
>
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I didn't realize that.  Thank you for correcting me.  It reminds me a 
bit of the really old drives (like 80 MEG capacity) that had several 
values you could use for sectors per track, depending on whether the 
partition in question was inside, middle, or outside of the disk.  Do 
you have any idea how the ZBR knows where to put the data when the 
tracks are different sizes?  I can't see any way of doing it without 
some fairly complicated math.