I wholeheartedly applaud this example of My Tax Dollars At Work!
https://www.canada.ca/en/conservation-institute/services/conservation-preser...
-Adam
Get Outlook for Androidhttps://aka.ms/AAb9ysg
On 2024-05-02 Adam Thompson wrote:
I wholeheartedly applaud this example of My Tax Dollars At Work!
https://www.canada.ca/en/conservation-institute/services/conservation-preser...
This is actually a very good article with lots of juicy info.
However, unless I'm missing something, they don't show the data to support their longevity conclusions in Table 2?
I started optical backups with my current automated method in 2003. A few years ago (so ~ 20 year old discs) I took out the first few hundred discs I burned (CD-R's at the time) and ran them through my checker. Only one had an issue and only on one ~80MB archive file. I have a db that has md5sums for every file so I can easily tell when a file isn't 100% perfect.
That's my empirical result: a 99.99[999...]% success rate on CD-R longevity. I think will go through the oldest ones again, as I was meaning to finish it and write a report... When I get free time, lol.
I'm intrigued that their chart puts the most common CD-Rs at double the life of common DVD-Rs! I hope that's not the case, as most of my checks have been of my oldest CD-Rs, because I didn't start DVD-Rs until much later when the price/GB crossed over. But it is something to take into account when I set my "re-burn after" tuneable.
I also have a very hard time believing stamped RO DVD (i.e. movies you buy at the store) are 10-20 years. I have a ton of DVDs that are more than 20 years old and have never seen a failure. Well, kids scratching them to heck does do them in, but never just bit rot.
Interesting that they put stamped CDs at 50-100, compared to DVD's 10-20... I wonder if the general longer life of CD* over DVD* has a lot to do with density and bpi (if there is such a thing in optical): less dense (more dye area per bit) being more forgiving?
I also have a vaaaast CD collection and follow things on discogs quite closely and can report that a miniscule number of (stamped) (music) CDs suffer bit rot, which jives with the 50-100 years in Table 2, because the oldest of these are around 40 years (yikes!). The notorious bit rot ones result in practically everyone's copy becoming an error-filled mess in roughly the same 5-10ish year window, usually after around 10-15 years. And they are almost certainly due to horrifically bad QA at the factory for a specific run, not a general failure of the CD technology itself.
And I'm finally exonerated!! People always thought I was completely nuts for only labelling my optical media in the inner circle miles away from any data-containing layer. (Now they'll just think I'm nuts for other reasons!)
As usual, if any member has old DVD-Rs doing nothing and want to donate to the Trevor Cordes Data Backup Project, bring them to a meeting!
Fantastic find, Adam! And great comments, Trevor.
From my early CD-R days onward, I exclusively used Verbatim DataLife (and later DataLife Plus) media, as they were the only ones that used a polymer instead of dyes, with projected life (of recorded data) of 100+ years.
Hartmut
On Thu 02 May 2024 at 00:02:49 -05:00, Trevor Cordes trevor@tecnopolis.ca wrote:
On 2024-05-02 Adam Thompson wrote:
I wholeheartedly applaud this example of My Tax Dollars At Work!
https://www.canada.ca/en/conservation-institute/services/conservation-preser...
This is actually a very good article with lots of juicy info.
However, unless I'm missing something, they don't show the data to support their longevity conclusions in Table 2?
I started optical backups with my current automated method in 2003. A few years ago (so ~ 20 year old discs) I took out the first few hundred discs I burned (CD-R's at the time) and ran them through my checker. Only one had an issue and only on one ~80MB archive file. I have a db that has md5sums for every file so I can easily tell when a file isn't 100% perfect.
That's my empirical result: a 99.99[999...]% success rate on CD-R longevity. I think will go through the oldest ones again, as I was meaning to finish it and write a report... When I get free time, lol.
I'm intrigued that their chart puts the most common CD-Rs at double the life of common DVD-Rs! I hope that's not the case, as most of my checks have been of my oldest CD-Rs, because I didn't start DVD-Rs until much later when the price/GB crossed over. But it is something to take into account when I set my "re-burn after" tuneable.
I also have a very hard time believing stamped RO DVD (i.e. movies you buy at the store) are 10-20 years. I have a ton of DVDs that are more than 20 years old and have never seen a failure. Well, kids scratching them to heck does do them in, but never just bit rot.
Interesting that they put stamped CDs at 50-100, compared to DVD's 10-20... I wonder if the general longer life of CD* over DVD* has a lot to do with density and bpi (if there is such a thing in optical): less dense (more dye area per bit) being more forgiving?
I also have a vaaaast CD collection and follow things on discogs quite closely and can report that a miniscule number of (stamped) (music) CDs suffer bit rot, which jives with the 50-100 years in Table 2, because the oldest of these are around 40 years (yikes!). The notorious bit rot ones result in practically everyone's copy becoming an error-filled mess in roughly the same 5-10ish year window, usually after around 10-15 years. And they are almost certainly due to horrifically bad QA at the factory for a specific run, not a general failure of the CD technology itself.
And I'm finally exonerated!! People always thought I was completely nuts for only labelling my optical media in the inner circle miles away from any data-containing layer. (Now they'll just think I'm nuts for other reasons!)
As usual, if any member has old DVD-Rs doing nothing and want to donate to the Trevor Cordes Data Backup Project, bring them to a meeting! _______________________________________________ Roundtable mailing list Roundtable@muug.ca https://muug.ca/mailman/listinfo/roundtable
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Adam Thompson -
Hartmut W Sager -
Trevor Cordes