Over the last month or so, I have been checking the integrity of my entire stash of CD/DVD-R media. It primarily refers to home burns, but also some discs I got as copies from friends etc. I relied primarily on the ScanDisc test in Nero CD DVD Speed 184.108.40.206. I've decided to share the results with you as some of you may find the results interesting.
To start, I offer two notes of caution
1) This is not a scientific study, rather a crude real world study.
2) The numbers are very rough, I had too many discs to keep exact records and do the tests in a timely fashion.
I chose the ScanDisc test as the fastest and most straightforward check of disc integrity. It reports sector groups in one of 3 ways - Green = Good, Red = lost, Yellow = Damaged.
A CD, and to a smaller extent, a DVD, has what are referred to under names such as redundant bits, checksum bits, subchannel data etc. That means that the data encoding scheme allows one, bit per octet, perhaps more, to fail, (i.e. a 0 becomes a 1 or vice versa). Anyone who for example, has ever tried to copy a SafeDisc (V2) protected disc, will know all about subchannel data as "weak" sectors are an essential part of that protection. I believe the ratio is 14 bits total per byte for CDs, but that for DVDs its a lot less.
I assume therefore that CD Speed reports "damaged" sectors where the algorithm shows bit failure, but the correctional margin is such that the data is still readable at full speed. If true, it adds much value to an already helpful test. It would also make it more valuable than a Transfer Rate Test in some respects.
Burn age varies from a few months to 8 years. Storage conditions ranged from written once and never used again, to read many times, to stored out in the garage, where the discs would have been subject to lower temperatures and higher humidity.
Based on the results of ScanDisc tests, I classified all the discs as in one of 4 conditions:
1) No unexplained non-green sectors: Good or, in the case of out-of-the-house storage, Survived.
2) Scanning in one DVD-RW drive showed damage, but the other found no problem: Borderline
3) Both my DVD-RWs saw a problem with the disc, but the data was readable: Damaged
4) Red sectors verifiably affecting data, or an attempt to read the disc resulting in CRC (Cyclical Redundancy Check) errors: Failed, Lost or Data Loss
What was at stake:
- roughly 250 CDs and DVDs
- 90-95% CD 5-10% DVD
- all DVDs are Philips branded, MBI and Infome(something, the scaner didn't report the full name).
- 60% approx CDs are CMC MAG, mainly Memorex, some Imation and some no-name brands.
- 25% approx CDs are Prodisc, mainly Memorex
- 5% approx CDs are Ritek
- 5% approx CDs are Tayio Yuden mainly Maxell and FujiFilm
- 5% approx CDs are MBO unbranded
- 5 approx discs are Moser Baer
- 2 discs were "Multi Media" cheap stuff from Aldi/Lidl
All tested with Nero CD-DVD Speed 220.127.116.11 ScanDisc
- 1 Moser Baer DVD discarded due to data loss
- 1 "Multi Media" CD discarded due to potential data loss
- 2 CMC MAG CDs from this stash had been written off 6-12 months previously due to data loss. These were branded "PC Line"
- About 20 CMC MAG CDs discarded due to verifiable damage
- Of those, Octron branded CDs from Lidl (all failed), followed by PC-Line brand (33% estimated lifetime failure), fared worst WRT failures and loss. By and large, Memorex and Imation CMCs discarded were still readable, but had clearly deteriorated.
- 1 CMC MAG CD recovered by the removal of a paper label I had put on it :doh:
- 2 "borderline case" CMC MAG CDs kept (i.e. one drive found damage the other didn't)
- 2 "borderline case" Prodisc CDs kept (ditto)
- All but 1 of Riteks were good, I had stored some in my garage - and one was damaged.
- All the Moser Baer CDs were good
- All Tayio Yudens (where the results made sense) were Good
- All the unbranded MPOs were good (but they're all relatively new)
- 1 Daxon, probably BenQ branded SURVIVED, up to 6 years storage in the garage, a paper label applied, stored in a paper envelope!
- 2 Gigastorage unbranded CDs survived a long time under various storage conditions.
Seperately, during the time I was doing this scan, I bought a 10 pack spindle of Lightscribe Verbatim MCC 004 DVD+Rs. Of those, 9/10 burned perfectly datawise, but 1 did have a surge of PI Failures towards the end, and did poorly in a TRT. The other 9 burned the best I've ever seen, with Quality Scanning showing very low PIF counts and TRTs passing with flying colors. Those 9 discs have performed even better, in some cases, than TYG 02 valueline media under the datasafe brand which I also obtained recently, also a 10 pack. But both are relatively new and so were not included in the main study.
1) CMC MAG has a certain reputation for being a "3rd rate" media manufacturer. My experience bears that out.
2) The quality of CMC MAG implementations vary - 'good' brandnames like Memorex will rarely let you down badly, but if you buy cheapo discs or own-brand discount labels backed by CMC - don't have any expectations as they will likely fail.
If you've ever bought discs in a European discount chain called "Lidl" check them out now - and back them up ASAP.
3) Prodisc, Ritek and Moser Baer CD-Rs are all of a better quality than I had expected - despite some of these being subject to years of storage in adverse conditions, they all held their data.
4) The only discs on which I had lost data after all these years were CMC MAG CDs and one Moser Baer India DVD.
5) The lowest levels of PI Failures I have ever seen on new burn DVDs were backed by MCC 004 AZO, followed not too far behind, by TYG02.