I’ve put a tiny piece of blue tape on Blu-ray disc with data, and, surprisingly, it was still fully readable (reading speed dropped at this place, that’s all).
Next, I’ve put a slightly bigger piece of tape on it, and it made ~15% of disc unreadable. Reading “damaged” areas is quite slow, so I interrupted ddrescue/dvdisaster when data reading speed dropped too low, and it was around 15%.
Both results are strange to me. First is almost too good to believe, second is too bad. Maybe data behind little piece of tape have been recovered by internal Error Correction Code? And big piece, sure it didn’t cover 15% of readable surface. Maybe full “recover” by ddrescue would have copied a lot more data, but I doubt it.
Why do you put tape on your disc?
I was trying to proof DVDisaster application works and will be able to recover missing data. I’ve failed to do so.
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Optical discs include quite a bit of redundancy, so even if some data is unreadable, it can be found in the readable parts.
I wonder how much tape you need to unbalance the disk until it’s completely unreadable?
Probably covering area close to inner circle will make entire disc unreadable.
The disk will remain readable more if the damage is a line from middle to edge than if it’s a ring around the whole disk.
