General stability of CD vs DVD, and recovery of data from corrupted discs

Below there is evidence to suggest that CDs won’t last forever.
Purchased in 1984 the first few tracks play with no problems however the later tracks, oh dear. :confused:

^^That is a stamped disc and in no way similar to a recordable. If Optical was a viable archival venture then large newtworks would not be using Tape as they currently do. If your serious about enterprise Archiving then RAID 5 and Tape is the safest route.

One CD doesn’t prove anything. I have 700 CDs some of them as old as 1983, and I have ripped all of them onto a harddrive. This means that I have tested the readability of all of these CDs. Out of the 700 CDs only 3 were difficult to read and only 1 was so bad I had to give up getting a bit-perfect rip and had to settle for a rip with inaudible errors (using error concealment).

The longevity of pressed media also has little to do with the longevity of recorded media. This doesn’t mean I think that recorded media will last longer than pressed media - it just means that they should not be compared directly.

Your making a false logical leap. Just because Television networks use tape for archiving doesn’t mean that all alternatives must therefore be unacceptable. It just means that tape works for them so far.

RAID-5 isn’t an archiving technology, it’s a way of keeping data available on-line with a somewhat fault-tolerant set of harddrives (the “R” in RAID-5 means Redundant).

The only way to make data stored on harddrives last longer than approx. 3-10 years is to move the data to new harddrives at regular intervals. This is equivalent to transferring data on your CDs or DVDs to new media every few years.

Hey, thanks to all for the additional opinions. It sounds like storing to optical media for longevity, plus dumping to a hard disc as an additional backup (and a convenience for occasional rapid access) is a great combo. Don’t think I have the bucks (or know-how) to go into tape systems right now. If I do eventually ever go to tape, then duplicates on hard disc would be even more important, given the search time needed on tapes.

I’m still hoping to hear some opinions on the read quality and the longevity of CD versus DVD - - comparing the top CD media (like TY) with the top DVD media. Any experiences, thoughts out there??

Thanks, again, for all the responses. They are really very helpful.

[QUOTE=DrageMester]

Your making a false logical leap. Just because Television networks use tape for archiving doesn’t mean that all alternatives must therefore be unacceptable. It just means that tape works for them so far.

Mmm, I wouldn’t say that TV networks are too hot as far as archiving goes. Any British music lovers will know the BBC ‘binned’ or ‘whipped’ most of the Top Of The Pops music archive from between the years 1964-1974, the sixties tapes were over 90% destroyed.
From the year 1966 only 1 track exists.
Performances destroyed include, Pink Floyd, David Bowie, The Walker Brothers…the list is endless. :sad:
Thank heavens other European networks were on the ball. :clap:

David Bowie performing ‘Space Oddity’ on the Swiss show ‘Hits A Gogo’ during November 1969.



@nicadair - wow, those text colours are hard to read (the green and the earlier turquoisey one) :eek:

Indeed but they are there to be used! :eek:

Hahaha wow shields eyes :bigsmile:

Although now getting a bit off topic, it isn’t just what medium you make your backup to, probably more importantly is how it is stored. Read through these forums and people who live in hot and humid places have a hard time with optical media. God only know what would happen to a magnetic tape stored in the middle of a rain forrest! Keep any back up in a nice cool, dark and dry place and it will last a lot longer! - guess that goes the same for paper archives too!!

It depends on a number of variables whether DVDs or CDs will last longer, and I don’t know if anyone has done a comprehensive test.

It is best to have 2 copies of each disc using different good quality brands (and dye types) stored in separate locations. This way one disc should last longer than the other.
Every couple of years check the physical condition of the discs and verify the data on them. If there is a problem then make a new copy from the good disc.
I would use DVDs due to the number of CDs needed to backup the same data. It is best to stick to single layer 4.7GB DVDs as it is more of a challenge for the drive to read from a double layer disc. Also +/-R discs are probably longer lasting than +/-RW types.
It would not be too much of a problem making a 2nd copy of 10 DVDs, but the same amount of data on CDs would be a pain to make a 2nd copy of.
Also one set of DVDs could be stored in a fire safe box, but the CDs probably would not all fit.
CDs have the reflective layer directly on the top surface of the disc, but DVDs have the reflective layer sandwiched inbetween two layers of plastic (even on single layer discs) so it is better protected from damage.

The quality of the discs is important, I had some cheap CD-Rs a few years ago that had a plain silver top face, when the top surface got scratched the reflective layer came off in large flakes. The reflective layer probably had very little protection from moisture either. Most CDs have a protective clear lacquer or white paint face ontop of the reflective layer but it is still more vunerable than in a DVD.
I use white face CDs now for better protection.

I decided to do a quick test, so have just tried scratching the top surface of a good quality white face CD with a screwdriver and it still removed the reflective layer, although the paint did provide some protection and also prevented as much flaking off.
The DVD reflective layer was not damaged despite deep gouges on the top plastic surface.
Scratches on the data side of DVDs and CDs can cause problems with reading, but the reflective layer is better protected on DVDs.


Scratched CD - top and data surface


Scratched DVD and top plastic layer removed showing undamaged reflective layer

It only takes 1 scratch to destroy any disc (regardless of which make it is), though it would certainly be foolish to archive anything on a re-writeable disc. :frowning:


I decided to test your statement, but one little scratch shouldn’t be enough to kill a DVD, so I made a handfull of scratches in that exact area, and they were about 2mm (0.08 inch) wide altogether.

None of these drives could recognize the disc: NEC 4551, BenQ 1655, LiteOn 165P6S, Pioneer DVR-111.

Verdict: Disc killed!

Then I tried making only a single but deep scratch in the same location on another disc. All of the same drives recognized the disc, and two of them read the disc without any slowdown (BenQ and Pioneer), the third drive (LiteOn) had a small dip in the reading transfer graph but nothing major. Only the NEC drive couldn’t read the entire disc.

Verdict: Disc wounded and in need of medical treatment.

So from this little experiement I’d say you’re mostly right, but perhaps exaggerating just a little bit. :slight_smile:

I had assumed that that area marked by nicadair was where the TOC was held.

Dragemester, in your tests did you try ISObuster to see whether the actual AV content could be recovered by circumventing the corrupted TOC?

No, it was just a quick and dirty test using Nero CD-DVD Speed to read the first 500 MB of the disc. I can test the “killed” disc with IsoBuster if you like.

Yeah - give it a go :flower:, because all the stuff I’ve read, and personal experience leads me to believe that ISObuster works on non-finalised discs (ie not ‘physically’ corrupted). A deep scratch in the main data area might result in the loss of information, but where the problem is in the TOC area it might be able to recover something from a full scan.

IIRC it has a mode which runs right through the disc and can detect content like VOBs for example, and will predict the correct file extension.

Gave it a go:

LiteOn and NEC drives with IsoBuster: No Media Present

Pioneer drive with IsoBuster: Blank CD (it’s actually a DVD)

BenQ drive: After inserting the disc again, the BenQ drive actually managed to recognize it and read the damn thing at 16x using CDSpeed Read Transfer test (the first few MB only at 5x CAV though)! :eek: :clap:

Verdict: The BenQ is a Necromancer and can talk to dead discs. :stuck_out_tongue:

That’s a shocking result…I’d never have thought it :eek:…mind you, having said that, I did once have a disc that my 1635S refused to even acknowledge, but my BenQ 1650 read it without a hitch.

Thanks for doing the tests, Drage :).

I work on the principle if DVD Decrypter cannot read a disc, nothing can.
I have use IsoBuster before to recover 2 un-finalised Verbatim DVD+Rs but it was no help.
I say un-finalised, my Philips DVD1000mk2 didn’t finalise them properly & there was some kind of error.
Needless to say I rarely use my DVDR1000mk these days.
It’s just an ornament. :frowning:

Thanks for doing the testing, Dragemester :flower: , and I am pleasantly surprised too by that result. In future will listen carefully to my 1640 for extra information coming from ‘The Other Side’… :wink:

I See Dead People…uh…Discs

Unfortunately there are some “living” discs that all my other drives can read, that the BenQ 1655 cannot read (some bad sectors). So it’s a mixed blessing.