tech-kern archive

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]

Re: DIOC{G,S}STRATEGY not implemented for all disk devices

On Mon, Jan 28, 2008 at 06:32:51PM -0800, Bill Stouder-Studenmund wrote:
 > The biggest issue I see with making CD random access slow is the fact that
 > CDs are CLV, not CAV. That's Constant Linear Velocity, not Constant
 > Angular Velocity. That means that the speed of the disk under the optical
 > head stays the same, not the rotational speed of the disk. So if you seek
 > from the inside to the outside such that your radius around the disk
 > doubles, the whole disk has to halve its rotational velocity. Changing the 
 > speed of the whole CD makes disk head seeks seem fast. :-)

My (vague) understanding is that CD speeds higher than some relatively
old point (8x maybe?) are actually CAV, and I would imagine this is
probably true of the newer disc types too, so this may not be much of
an issue.

Of course, I could be entirely wrong :-)

David A. Holland

Home | Main Index | Thread Index | Old Index