I/O errors reading DVD-Rs but DVD+Rs are OK
 

I have a very strange problem only on one machine (a Dell DX-260 I believe). I am paranoid so when I make backups I always make 2 copies one on DVD-R and one on a DVD+R. I also always verify the copies after I burn them. This is where the problem occurs. On this machine the DVD-R almost always gets an I/O error. Yet the DVD+R almost never does. I can take the DVD-R to another machine and it will read just fine. So I thought, the Samsung combo drive was bad and replaced it with a Samsung DVD+/-RW drive. It however has the same exact problem, DVD+Rs read fine DVD-Rs get I/O errors. The odd thing is that if I boot the same machine (with the same DVD drive) in Windows there are no I/O errors on the DVD-Rs. Is there something different about DVD-Rs that would cause a problem like this?

I have been having a similar problem - but not identical. I have an hp pavilion a720n with an hp dvd writer / cd-writer combo. I can burn DVD's and CD's just fine with the buner, but when I try to read the newly burnt CD back in with the same device I get read errors and files are corrupted. However, the CD is really fine and can be read normally on a simple cd-rom reader on the same computer, with no read errors. Every time I 'mount' the CD on the dvd combo unit, different files are corrupted when read. The same combo unit works perfectly well under windows xp (the computer is dual booted, with XP, and with debian unstable as my linux system). I suspect something is wrong with the ide-cd module that kernel 2.6 uses, but I'm no programmer. I suppose it could be a hardware issue (bad combo drive), but it is working perfectly under windows xp (both burning and reading disks), so I doubt that.

Sorry, I have no solution - other than to burn CD's with the combo unit, and read them in with the cd-rom unit. Not an elegant solution. I'm hoping a future kernel update will magically fix the problem.

I have no problems with black Memorex DVD-R 4X discs with Pioneer DVR-106D using a 2.6.10 kernel. Both data and video work fine in many DVD readers. Many DVD-R and DVD+R discs do not comply to the standards so they will fail eventually. An article that describes about the performance of many DVD recordable discs go to DVD http://www.xbitlabs.com/articles/sto...dvd-discs.html. The best DVD and CD recordable brand is Plextor.

Problem fixed (I think)
 

(I am the one who made the original post)

Let me describe the symptoms again (because there were more symptoms than I had in the original post):

* I/O errors when reading both DVD-Rs and DVD+Rs, not everytime but very often.
* Reading a DVD brought the machine to it's knees, even if you used 'nice' to lower the priority. Doing something like "nice diff -rs /media/dvdrecorder /original/source/directory" made the machine practically unusable for anything else. It would take 15 to 30 seconds to switch virtual desktops and sometimes a minute to render a web page. This was on a Dell GX260 with a 2.0 GHz Pentium 4. I could do the same thing on a Dell GX150 with a 800 MHz Celeron and notice just a slight slowdown.
* Almost every DVD I tried to burn with this machine turned into a coaster, even when burning at the slowest speed possible. I finally gave up using it to burn DVDs and only burned CDs at the slowest speed and even that sometimes failed. I didn't dare even touch the machine while it was burning.
* I replaced the DVD-R drive with 3 or 4 different drives (both Samsung and Sony) and had similar problems with all of them. None of the drives I tried worked well.
* I tried several of different versions of Linux (Fedora Core 2 and 3, SuSE 9.1 and 9.2).

I believe I have found the problem and do I ever feel stupid that it has taken months to figure this out.

DMA was turned off on the drive (Doh!):

$> cat /proc/ide/hdc/settings
Password:
name value min max mode
---- ----- --- --- ----
current_speed 0 0 70 rw
dsc_overlap 0 0 1 rw
init_speed 0 0 70 rw
io_32bit 0 0 3 rw
keepsettings 0 0 1 rw
nice1 1 0 1 rw
number 2 0 3 rw
pio_mode write-only 0 255 w
unmaskirq 0 0 1 rw
using_dma 0 0 1 rw

I then used YaST -> Hardware -> IDE DMA Mode to set /dev/hdc to DMA On (default mode) and voila it is working much better.

name value min max mode
---- ----- --- --- ----
current_speed 66 0 70 rw
dsc_overlap 0 0 1 rw
init_speed 66 0 70 rw
io_32bit 0 0 3 rw
keepsettings 0 0 1 rw
nice1 1 0 1 rw
number 2 0 3 rw
pio_mode write-only 0 255 w
unmaskirq 0 0 1 rw
using_dma 1 0 1 rw

And now I can do "diff -rs /media/dvdrecorder /original/source/directory" and I can't even tell it's running and so far no I/O errors.