A Starter's guide on recovering damaged and rotten CDs
secnigma.wordpress.com
secnigma.wordpress.com
My biggest savior was a Pioneer BDR-AD07BK which managed to read some discs that other drives couldn't even get the TOC off!
I wrote a gnu-ddrescue wrapper back then to avoid accidentally resuming a read to the wrong iso (only ever tested on alpine): https://github.com/9001/usr-local-bin/blob/master/miso
This is also the reason why all-over-print CDs are better survivors than discs whose obverse design integrates the raw silver. Note that this is specific to CDs — DVDs and BDs have protection on both sides!
I ran ddrescue on two different DVD drives and a blu-ray drive, up to the point where 48 hours would pass with no new data recovered. This left me with still several minutes of video that was unwatchable.
I solved it by spending about $12 to get used copies of all 3, which ripped fine. Any idea(s) that I could try had that option not been available?
Can't store some data reliably for a long time? You can mitigate it by storing some other data reliably for a long time.
The first option may be technically more sound but comes with a larger investment in terms of time and money. Second option may be less reliable but with significant savings. It's up to the owner of the data to decide how to balance these.
You'd be comparing to an old optical disc. So almost anything is higher reliability than that, starting with a newer optical disc and probably ending at any cloud storage.
> does a consumer have
This isn't limited just to your average consumer. DVDs are still in use in libraries and different archives which can't afford to store a full backup.
We've had parity checks appended to the very same data to be protected for so long because it does protect from some common failure modes even if not from all. Dvdisaster goes one step beyond and gives the option to store the ECC file elsewhere. Definitely better than nothing and probably even with a very good cost/benefit ratio.
Is "cloud" really being considered as a viable backup solution?
I mean, some of my CDs are older than most of today's "cloud" servers and can be read just fine.
And if you're happy being able to recover "some" of your data that's a perfectly legitimate option. Write CDs and DVDs, save to HDDs and SSDs, to the cloud, print on paper, or a combination of all. Only you know your data and its importance.
But what you'll want to ask yourself though is how many CDs written since than can't be read just fine. I have books from before electricity was a thing and still am thoroughly convinced paper is not the best for long term preservation.
My oldest cloud stored data that I can verify is a 25 year old email in my Yahoo mailbox. I have stamped CDs that survived that long, no written CD that I can think of.
The point is that it's impossible to try and predict how the cloud will look like in the future. One day we can end up receiving an e-mail that we need to download all data from the cloud because they're ending their operation. And the future of paper/CDs can be predicted easily.
If anyone's worried about the lifespan of CDs, it's always possible to copy the collection once every few years.
Also I think that paper could be a viable backup solution, at least for e.g. family photos -- print, encapsulate, hide in a dark and dry place.
You don't and trying to guess which technology or provider will still exist in 25 years is probably pointless.
If you want to keep your data for extended periods of time (decades) the best strategy is to a) define what you want to protect against and don't go for "everything" or it will be prohibitively expensive and impractical, b) have at least one redundancy (an ECC file, a full copy, whatever helps you recover the data if one data set is affected), and c) ensure that the data sets cannot fail at the same time, statistically speaking, by using completely different methods.
A CD will fail suddenly because you probably can't check it often enough. A major cloud provider doesn't disappear over night though. Keep the parity file in two completely unrelated clouds maybe even for free, or keep the whole data in highly compressed archives with recovery record in multiple clouds for a cost. Keep a full copy of your data on different HDDs with (different?) resilient file systems, and connect them periodically for a sanity check. Check periodically that you can still use the data, having an intact file isn't enough if you can no longer open that format used in 1993.
There is no one size fits all and the is no set and forget "this backup will be guaranteed for the lifetime of the universe" answer. Choose what you protect against and choose how much you're willing to pay in time, effort, money. Then play whack-a-mole as some of your backups are no longer viable and you replace them to always have that +1 minimum resilience.
I'm surprised by that, yahoo mail has went through several cycles of randomly deleting people's emails and contacts. I think of of the times they did it to me, it was because I hadn't logged in within 90 days.
Yes, by some people. Who later ask on HN how to recover their data from Google Cloud or Azure. /s
8TB HDDs can be had for around $100 each. Four of these in RAID5 gives you 24TB. That's enough to backup 5000 DVDs (single layer) or 2800 dual layer DVDs.
If you're protecting your data from minor damage and decay of the DVD that stores it, having an ECC file stored elsewhere (a newer DVD, or HDD, or cloud) is the lowest effort and cost option but still a big step forward in resilience. It doesn't matter how long each medium lasts, all that matters is that they don't fail at the same time. Pick your HDDs from different manufacturers, models, or batches and the chance that all fail within the same short time period without external influence are exceptionally low. And when one does fail you replace it. You'll never get a one time perfect solution, you're just buying time to rebuild your resilience when you take a hit.
If you're protecting against the complete destruction of the disk then an ECC file won't do, you'll need a full copy. Or multiple copies, and in multiple locations. Or on different mediums with very different reliability curves. You might want to protect against internal or external malicious actions, technical obsolescence of the medium or data format, vendor lock-in, or political instability. No one size fits all solution, certainly not a cost conscious one.
For my dad, and anyone just tech-savvy enough to select a bunch of files, put a disk in the drive and click "burn", the choices are either DVD (which deteriorates) or a cloud solution. Anything else is too much, including "here's a NAS, it'll last you forever as long as you keep it plugged in".
Then you moved to the (unsupported) argument that consumers don't have reliable options. Then to the (unsupported) argument that hard drives fail after 5 years. Then to the argument that some users are not tech savvy enough to use anything more complex than a CD.
The last one is the only realistic yet still relatively weak complaint. It doesn't invalidate in any way the option proposed in the article. Looking at dvdisaster creating an ECC file is at most just as complicated as generating the data you're looking to protect. Using a commercial cloud storage solution is equally straight forward. A consumer friendly NAS is very easy to use while not so obvious how to fix in case of failure but that's why you're there to set it up and set a sync to the cloud(s).
I hope you taught your father how to select appropriate quality media blanks, what are the optimum storage conditions, how often to check that the data is still readable, what to do when a disc becomes unreadable or very hard to read, how to replace the optical drive when it fails or there's dirt on the lens, and so on.
Wasn't able to easily decline cookies.
It was really handy to get scraps off a disc that was very damaged.