SATA DVD speed's too slow (Modified by Joshua Isom)

[Andresen, Jason R.]

From: owner-freebsd-hackers at freebsd.org
[mailto:owner-freebsd-hackers at freebsd.org] On Behalf Of Joshua Isom
>
>Redirected from freebsd-questions after no reply.
>
>I currently have an SATA DVD-RW drive for my computer.  I have to boot

>using a CURRENT kernel to get the drive recognized, and dmesg lists it

>as running at 3.3MB/s.  Running mplayer -dumpstream gets around 3 megs

>a second.  Copying off a data dvd gets about the same.  But I recall 
>reading about playing a dvd before trying to get the data off of it 
>when using dd, and it seems to work.  But the odd part is, it can get 
>up to 20 megabytes a second.  Does anyone know how to get the higher 
>speeds all the time?

What you're probably seeing is a feature of how modern optical drives
work.  Unlike the "4x" drives of old, the drive does not speed up or
slow down the disc based on the position of the head, instead they
maintain a fixed rotation speed.  Because of this, the pits on the edge
of the disc move much faster than the ones near the center of the disc.
As you write to the disc you will see your speed increase as the laser
gets closer to the edge.  Of course the drive manufacturers advertise
the speed of reading/writing the outermost track when selling the
drive.