I have an LG BD-RE WH14NS40 DVD writer which has worked fine on CDs, DVDs and single-layer bluray disks. I got some RiDATA BD-R DL blanks, and I got the drive to write to it, but the disk could not be read. How can I tell if the disks are bad or the writer is not capable of writing to dual-layer disks?
All suggestions are welcome. I was using K3B on Ubuntu 20.04.
Thanks, Jon

Maybe get a bluray disc and see if you can read it like a movie or other tested good data. (assumes you can read movies here)

There is some command line that can report what the drive may be capable of. I forget it.

The drive IS capable of dual-layer bluray, but I'm trying to determine if it works well recording on dual-layer, or if the blank media I have are crummy.
I can read and write single-layer bluray just FINE!
A lot of people online suggest using Pioneer drives and Verbatim media for dual-layer, I'm just trying to find out which of these I need to replace.
Thanks,
Jon

When I open my dvd writer tray, I see a laser pointing up. That gathers dust, aided and abetted by static. Often a wipe helps.

For my sins, I maintained a dvd pressing machine in the late nineties. The tech on blu-ray is stretched to the limit. How old is your drive?

EDIT: The command is

There is only one way: you need to try it. How old is this device? Probably it is just a bit dirty inside, or went wrong. Also CDs and DVDs have a relatively short lifespan.

There is no way to even see the optical head, it is behind the spindle. The drive is entirely enclosed, you'd have to take the entire case of the drive apart. I have done this with old CD drives, but I don't really want to tear this one apart. This writer is a few years old, but has not been used a whole lot. it still works fine on standard bluray disks, the only trouble I am having is with dual-layer.
The hdparm command gave :
dev/sr0:
SG_IO: bad/missing sense data, sb[]: 70 00 00 00 00 00 00 0a 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

ATA device, with non-removable media
Standards:
Likely used: 1
Configuration:
Logical max current
cylinders 0 0
heads 0 0
sectors/track 0 0
--
Logical/Physical Sector size: 512 bytes
device size with M = 1024*1024: 0 MBytes
device size with M = 1000*1000: 0 MBytes
cache/buffer size = unknown
Capabilities:
IORDY not likely
Cannot perform double-word IO
R/W multiple sector transfer: not supported
DMA: not supported
PIO: pio0

Which doesn't tell me a whole lot.
Thanks,
Jon

Ok, the standard test back in the 1990s was a BLER test, a BLock ERror test. We used to use it for pressed disks. It was a windows utility. The Block error rate was never zero, but there was triple redundancy in CDs, so that didn't matter. But the BLER test counted the failures where the 2nd or 3rd copy had to be read.

I don't know of the linux equivalent. But with Blu-Ray, the physical medium is the same size, the density is way up, so the margin for error is way down. Things like fingerprints, the cloth used to wipe the disk, the laser, mechanical wear can all cause your issues.

If one side of the disc regularly reads and the other regularly refuses, what happens when you put a single sided disc upside down? Divide & Conquer. Lastly if you can't see the laser, how come the laser can see the disk? There has to be a way for the laser to read all tracks, inside to outside. If the laser is covered, there will be a slot in that cover.

EDIT: The hdparm command told me you didn't have a disk in.

I think you are thinking about laptop-style drives, this is a desktop internal drive, and has a solid metal case that completely encloses everything. When the loading tray slides out, you can just barely see the spindle hub, and the read/write head is on a carriage behind that.
I get the same result, I think, WITH a disk in!
/dev/sr0:
SG_IO: bad/missing sense data, sb[]: 70 00 00 00 00 00 00 0a 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

ATA device, with non-removable media
Standards:
Likely used: 1
Configuration:
Logical max current
cylinders 0 0
heads 0 0
sectors/track 0 0
--
Logical/Physical Sector size: 512 bytes
device size with M = 1024*1024: 0 MBytes
device size with M = 1000*1000: 0 MBytes
cache/buffer size = unknown
Capabilities:
IORDY not likely
Cannot perform double-word IO
R/W multiple sector transfer: not supported
DMA: not supported
PIO: pio0

I get an error message when insering the DVD I wrote yesterday.
I just ordered some Verbatim blank disks to see if they work better.
Thanks,
Jon

there is a way to clean it like this: https://www.amazon.com/Maxell-190059.../dp/B00000JPPI although I have no idea if it really helps.

I'm no expert on blu-ray and have decided I'm not ever going there.

The hdparm output is unsettling. I have a dysfunctional dvd drive which neither reads or writes, but it doesn't throw me errors from hdparm. It's over to you, but the drive itself is my suspect

Well, these are disks that I recorded, but DON'T work! So, maybe that is why I get that output. I have ordered some Verbatim blanks, we will see what happens with them. I'm afraid to use a cleaner disk, it could do more harm than good.
Thanks,
Jon

The cleaner disks I am familiar with are nothing more than an optical disk blank with a small set of brushes attached to wipe any dust or debris off the laser head and are never a risk in using them since they do their job while the drive is trying to access the disk when it is inserted.

A disk cleaner, OTOH is a device that is designed to polish the surface of an optical disk that may have gotten scratched or marred by mishandling and they do work if the damage is not too severe on a CD or DVD. I have never tried one on a BluRay disk.

Well, I got the Verbatim brand blanks today, and K3b bombed on writing that one, too. When I tried to reload the partially written disk, the drive just kept whirring and chugging, but never completed loading it as the system would see it.
So, now I am going to have to replace the DVD writer, or just give up on the dual-layer stuff.
Jon

To simplify things you might consider a USB BDRW drive. I have one and the biggest advantage to it is that it can be used on any system, is portable, and is powered from the usb port. It does require a USB 3 port, but most newer systems already have that so no big deal.

Having worked in a pressed disc factory, my advice is give up.

Electronics can get very small, but mechanics can't. For example, they can't have ball bearings with absolutely no sideways movement in them. Now they stick a drop of oil on it, and you can't feel anything, but you can have all the oil on one side or the other, which means movement.