[KLUG Members] re: Revolutionary CD Drives & Rotations Per Minute (RPM)

[Adam Williams]

> 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.