Long-ish post, skip to part 2 if you don't care for a backstory. This is kind of a rough draft, excuse me for that. I tried to be as clear as possible. TL;DR clarification at very bottom.
1. What happens when you trust DVDs too much.
My data is important to me. So like any other reasonable person, I regularly backup my data off of my harddrive to ensure that I don't lose it. I don't put my files and information on other harddrives, but on numbered DVDs which I store in a secure place.
This has always made me feel safe, because I have always thought that DVDs weren't prone to the same failures as Harddrives. I thought that once I got my files on a DVD and took care of it, I wouldn't have to worry about losing them. Recently I found out I was wrong.
A few days ago, I burned some really rare files onto a DVD using Nero. Nothing unusual, I've done this many times before, I just made sure I was extra delicate with those DVDs. Nero finished burning without a problem, I tested a few files on the disk by opening them, and everything was OK.
Yesterday I pop the disk back in again, looking to copy one of the files off of the same disk and it doesn't work. The computer actually freezes trying to copy or open this file, and I have to resort to ejecting the disk. After ejecting the disk, I get a dreadful message telling me that there was a read error. I'm shocked. I try opening and copying other files on the same disk, in the same subfolder and they work fine. So I figure that some files work, and some files don't.
Normally, I'd just burn another DVD and test all the files this time to be safe. Only one problem: all the files on this DVD are no longer on my harddrive. Also, they came from numerous sources, some of which no longer exist. Damn.
Now I'm stumped as to what I should do, and I'm quite angry that this happened so easily without warning. When I think about it, I worry that there may be other disks with faulty files that I'm not even aware of yet. Some of these may be recoverable, others may be gone forever. Today I appreciate all the times I've had burns that failed at 80% and up due to a write error, even though that would piss me off.
2. Ways to guard against burns that silently fail.
Preventing this from ever happening again is a top priority of mine. But how?
There are two factors that come into this for me: Reliability and Time. How much can I trust any solution to tell me that the files on the DVD will work? Also, regardless of whether this is done before or after burning: how long will it take?
If a solution is really, really reliable but takes 30 minutes to an hour per DVD, that's a bad solution. If it's fast as hell, but has a high chance of lying to me, that's also a bad solution. I care about my data being accessible after I burn it, but I don't have that much time to waste as well. I'm a (soon to be) college student with only one computer, one DVD burner and a ton of files on a small harddrive.
Here are ideas that I have been thinking about, and I will share them with you, however primitive they may be. If you know of something better, or have something to recommend, please share it. That's what I made this thread for.
- Make a text file with the CRC's of each file before it gets burned. After the DVD is burned, compare all the CRC's on the DVD with those in the text file. If they all check out, disk is good. If a few fail, the disk is bad, re-burn.
1a. Assuming that a file on a DVD will have a different CRC when it can be copied/read, and when it cannot be copied/read. If this isn't the case, then this method is worthless.
- A small script would be ran, and it would try to successfully "open" then "close" each file on the DVD one by one. All it would do is see if a file can be opened. The script wouldn't actually open an mp3 or movie and play through it, or try to run an .exe.
2a. In my mind, what makes this different from the first method is that you aren't doing any deep or intensive scanning, just a quick open() and close(). Quicker than CRC's right?
- Just find a better way to burn. It's possible that the previous two methods are unnecessary, and all I need to do is enable a magical option that makes sure no faulty data gets to the disk. Maybe, but there's already some basic error-checking going on during burning (or else why would Write Errors exist?) and I don't know how I feel about putting my faith in 'better error-checking' even if it did exist. I feel that the burner has failed me, and I can't really trust it. I'm still open to this if you can convince me I'm wrong in doubting it.
Burned a DVD with Nero, that 'successfully completed' with no errors. A few days later I am unable to copy/read/open files from this 'successfully completed' DVD. Now I'm looking for an automatic solution that will test files during or after burning and tell me if those files can or cannot be copied/read/opened.
Please don't ask "Why can't you open all the files yourself? hurrrrrrrr" I'd like to see you do that with thousands of files, one by one.