Billie Walsh wrote:
>
I've also had the problem with some disks. I'm not certain, but it
seems to me that if I leave a pack of disks in sunlight for a few
hours the top disk doesn't burn. Could be a red herring, but...
Think about how a CD works. There are two layers of clear plastic with
metalized sheet in between.
Not so. They're one clear plastic disk. The read/write side is
clear plastic, the 'label' side is a coating over the writable media
surface. This is why it can often ruin a CDr to use a marker or a
label with improper glue on the 'label' side. IOW's, the 'label'
side is the read/write side an is to be even more protected than the
underside. Often very cheap 'generic' brands have a very fragile
coating side. Many well name brand names, only had another layer of
coating with their logo over the manufacturers coating.
When a laser hits the metalized layer it
darkens it. These little dark spots, or lack there of, make all the 1's
and 0's. Now if you leave on out in the sun for a little while guess
what happens. A laser is really nothing more than light. A lot more
focused and locally intense, but light.
I bought a LARGE pack of CD's from a national computer store, won't
mention the name but it ends in USA. Almost half the discs were
unusable. AND, I never knew that CD's had to be formated but everyone
had to be formated before burning. Finally got through that and bought a
pack with a better brand name. Much better result. Can't say I didn't
make a coaster or two out of them but they were good to start with.
I guess it's true: "Caveat Emptor". You Do get what you pay for.
While you usually 'get what you pay for', buying CDr's is a
guessing game. Brand names don't matter as they very rarely make
the disks anyhow. Neither does where you but them matter very much.
There's hundreds of "Brand names", but only a handful of
manufacturers. Often one brand sells disks from several
manufacturers. EG, you can buy a 100-spindle branded Memorex or
Imation, only to find that out of the 100, they may be from several
different vendors. Like Prodisc, CMC magnetics, Ritek, Taiyo-Yuden,
Moser Baer India Limited, etc. Or you find a 'brand' that works
well, only to find the next spindle you buy is from a completely
different manufacturer(s).
The only way to tell what you've got is after you've bought them
with a blank in your burner, 'cdrecord dev=ATA:1,1,0 --atip'
(preferably as root).
As to burning, a good rule of thumb for data or audio CDr's is
not to exceed the lesser of 1/2 the rating of your burner, or the
media your using. EG, for 52x burner, 48x media.. burn at 24x max.
For important disks like install media, burn at 1/3, or 16x.
2.6.x kernels do not accept burning as user, unless they are
hacked to allow user into kernel space. Those hacks still don't
allow direct access to some kernel functions, an altho you might not
see the errors in a GUI, you are running a high risk of buffer
underruns, an a failed burn, or reading afterwards.
Of course, cheap, non compliant burners (like shipped with most
ready mades an laptops), combined with cheap media (like Moser which
are non orange forum compliant) is also a high risk for failed
burns, or reading afterwards.
--
Tom Brinkman Corpus Christi, Texas
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