The question how to (long-term) store our immense amounts of data is largely unsolved. Some text can be engraved into stone (or pure platinum). That should last! But it won’t store our audio or even video data. Even if limiting us to the most important (however defined) half percent of all existing data, we’ll have a hard time storing it that way.
Common digital storage has increased capacity to insane values… so has the amount of data lost without warning. I personally don’t trust current flash memory (USB sticks, SD cards) as far as I could throw them… and I’m bad at throwing. The only thing that can prevent sudden data loss is backup. My cynical signature is there for a reason.
How long a thing is going to last… we know it in hindsight only (aging simulation with heat, UV light and humidity gives limited information; not bad, but not beyond any doubts)
There was a time when seemingly everybody backed up their data to CD-R (or moved it there when the HDD was full). Nowadays most people look at optical discs with condescending statements “having left this behind for (better) modern alternatives” and “discs rotting away in no time anyway”
Is that so? Do CD-R rot away in no time? I mean: Beyond anecdotal incidents of a bad batch that behaved exactly like this (I’ve had such myself → garbage right from the beginning).
Now to the current example:
By coincidence I received 46 CD-R used to store MP3 versions of various audio dramas and audio books (with about 500 normal, pressed originals audio CDs). People are freeing their storage… ‘cause streaming-
rulez… to my advantage as a complete stranger was happy to give me his collection for just a crate of beer. Super friendly guy! Big “Thank you!” for him.
The CD-R in question are in my possession since a few days only and I took the opportunity to analyze them as good as possible. According to the file dates the discs have been burned between 2004 and 2007, which isn’t extremely old, but also not new. A significant age for digital archival(?) media. Archival is the keyword here. I would strongly recommend using archival grade discs for long-term storage… and most people will just repeat what they heard: Cheap discs will fail really fast. Still the cheap discs were sold the most. The odds of encountering actual archival discs are low.
All in all not the best conditions for long archive duration, but I’ve seen worse (like a bunch of loose PlayStation 2 discs in a cardboard box scratching each other up while moving the box)
Three different kinds of discs with only two different media IDs in ATIP:
If we were talking about other data, like executable files or zip archives, any corruption would be 100% loss. In this case everything under "damaged" would be data loss as well. In case of fault tolerant MP3 files a certain amount of noise can be tolerated (can still understand content).
The CD-R have definitely reached their end of life. Most errors occurred on the outer part (seems it is eating itself from outside in). Those discs contaminated with mold are the ones that failed.
For extracting data I used four optical drives. That increased success in recovering damaged parts compared to only one drive. Biggest surprise was, that the damaged Prodisc could be read the best by the cheap external slim DVD-RAM drive, while it wouldn't even detect(!) some of the Daxon.
For the bad circumstances this is a welcome surprise. I always recommend burning at least two backups on two different kinds of blanks (preferably with different, good writers). This in conjunction to additional error correction like Dvdisaster would have prevented any loss in 15+ years. Something that I cannot say of USB sticks and SD cards, which corrupted from one second to another for no apparent reason… or just would not be detected at all anymore, no matter what I tried.
I have to add a picture from Nero Disc Speed though. C1/C2 scanning reveals that the capabilities of the error correction are at the limit. Here is an example of a CD-R that gets read with full speed with no data loss:
On the outer edge corruption started creeping in. In not so distant future this CD-R will fail.
Even today I would recommend CD-R, DVD±R and BD-R as additional(!!) backup for important, irreplaceable files. Keywords here are: Cold storage, resistance against ransomware, offsite backup. A burned disc could save you from losing data. Chances for survival of two or three decades are very good when paying attention to some pieces of advise:
Thanks for reading!
Common digital storage has increased capacity to insane values… so has the amount of data lost without warning. I personally don’t trust current flash memory (USB sticks, SD cards) as far as I could throw them… and I’m bad at throwing. The only thing that can prevent sudden data loss is backup. My cynical signature is there for a reason.
How long a thing is going to last… we know it in hindsight only (aging simulation with heat, UV light and humidity gives limited information; not bad, but not beyond any doubts)
There was a time when seemingly everybody backed up their data to CD-R (or moved it there when the HDD was full). Nowadays most people look at optical discs with condescending statements “having left this behind for (better) modern alternatives” and “discs rotting away in no time anyway”
Is that so? Do CD-R rot away in no time? I mean: Beyond anecdotal incidents of a bad batch that behaved exactly like this (I’ve had such myself → garbage right from the beginning).
Now to the current example:
How do CD-R fare when used as archive medium?
By coincidence I received 46 CD-R used to store MP3 versions of various audio dramas and audio books (with about 500 normal, pressed originals audio CDs). People are freeing their storage… ‘cause streaming-
rulez… to my advantage as a complete stranger was happy to give me his collection for just a crate of beer. Super friendly guy! Big “Thank you!” for him.The CD-R in question are in my possession since a few days only and I took the opportunity to analyze them as good as possible. According to the file dates the discs have been burned between 2004 and 2007, which isn’t extremely old, but also not new. A significant age for digital archival(?) media. Archival is the keyword here. I would strongly recommend using archival grade discs for long-term storage… and most people will just repeat what they heard: Cheap discs will fail really fast. Still the cheap discs were sold the most. The odds of encountering actual archival discs are low.
Conditions:
- Cheap CD-R without any label on them from factory on (shiny from both sides) Virtually no protection against chemical/physical influence from above (bad)
- Storage conditions: Mostly unknown (???)
- Cellar was mentioned (bad)
- Some indication of water or moisture damage: mold (bad) →
- Individual jewel or slim cases (good)
- Signs of usage: Almost none. No scratches worth mentioning. (good)
All in all not the best conditions for long archive duration, but I’ve seen worse (like a bunch of loose PlayStation 2 discs in a cardboard box scratching each other up while moving the box)
Results:
Prepared for the worst I got way more positive results than expected. Most CD-R were readable from start to finish. Here are the exact numbers:| Total number of MP3 files | 805 |
| Recovered with Alcohol120% (audible damage in few places) | 4 |
| Completely lost files (100% loss or too much damage) | 6 |
| Total Data (Bytes) | 31,005,988,377 |
| Data lost (Bytes) | 298,361,278 |
| Data lost (percentage) | ≈0.96% |
Three different kinds of discs with only two different media IDs in ATIP:
| Total | Slightly damaged | Loss of file(s) | |
| Daxon 97m22s67f (blank) | 21 | 2 | 0 |
| Prodisc 97m32s19f (with factory label) | 3 | 0 | 0 |
| Prodisc 97m32s19f (blank) | 22 | 2 | 4 |
If we were talking about other data, like executable files or zip archives, any corruption would be 100% loss. In this case everything under "damaged" would be data loss as well. In case of fault tolerant MP3 files a certain amount of noise can be tolerated (can still understand content).
The CD-R have definitely reached their end of life. Most errors occurred on the outer part (seems it is eating itself from outside in). Those discs contaminated with mold are the ones that failed.
(Click for full-size)
Handwriting (not mine!) pixelated for privacy reasons.
Sorry: Microscope camera is crappy low-res thing. No better resolution available. Still impressive picture. Was even more impressive looking through the microscope myself.
Disgusting mold!
Handwriting (not mine!) pixelated for privacy reasons.
Sorry: Microscope camera is crappy low-res thing. No better resolution available. Still impressive picture. Was even more impressive looking through the microscope myself.
Disgusting mold!
For extracting data I used four optical drives. That increased success in recovering damaged parts compared to only one drive. Biggest surprise was, that the damaged Prodisc could be read the best by the cheap external slim DVD-RAM drive, while it wouldn't even detect(!) some of the Daxon.
Conclusions
For the bad circumstances this is a welcome surprise. I always recommend burning at least two backups on two different kinds of blanks (preferably with different, good writers). This in conjunction to additional error correction like Dvdisaster would have prevented any loss in 15+ years. Something that I cannot say of USB sticks and SD cards, which corrupted from one second to another for no apparent reason… or just would not be detected at all anymore, no matter what I tried.
I have to add a picture from Nero Disc Speed though. C1/C2 scanning reveals that the capabilities of the error correction are at the limit. Here is an example of a CD-R that gets read with full speed with no data loss:
On the outer edge corruption started creeping in. In not so distant future this CD-R will fail.
Even today I would recommend CD-R, DVD±R and BD-R as additional(!!) backup for important, irreplaceable files. Keywords here are: Cold storage, resistance against ransomware, offsite backup. A burned disc could save you from losing data. Chances for survival of two or three decades are very good when paying attention to some pieces of advise:
- More than one copy
- More than one brand
- More than one writer
- Cool (not ice cold), dry and dark storage
- Store in good cases, discs standing
- Regularly check for errors, create new copy when failure rate increases
Thanks for reading!
