Monday, August 21, 2006

08/21/06: Archive Tip - Check Your Discs!

Archive Tip - Check Your (Burnt) Discs!

I'm a big fan of backing up files. However, any photographer that has taken a significant quantity of photos will probably tell you that it's a lot of work to keep up with the file back-up process.

I tend to backup all of my client images as soon as they are uploaded -- I'll make 2 sets of discs. One set for local storage and one set for off-site. Once the images are post-processed, I'll make 2 more sets. And finally (well, it's never final when it comes to backing up files!), I make month-end back-up discs of everything I shot that month.

I've had a number of CD / DVD burners over the past 9 years (I think the count is up to 7...on 3 different PCs!) and I definitely have given each a workout. When I burn a disc, my data verification process involves popping the finished (burnt) disc into another drive (not the one it was burned on) and verifying that the data successfully copied. Previously I just verified the # of files and that the first and last files in my backup job appeared on the disc. That was until I discovered what a CRC error is.

A CRC, or "cyclic redundancy check" error means that files on your media were corrupted during the burn process. This happens when the buffer in the burn process can't keep up with the write speed of the drive. I had one of these CRC error discs earlier this month -- it was the first time I'd ever seen this error. And it also happened to come from a disc I burned on a fairly new laptop -- one that doesn't use Nero CD / DVD burning software. I like Nero because of the buffer under-run protection utility. I've always had good luck with Nero creating good data files on recordable media. My new laptop uses another software application for burning discs. I guess you could say I got "burned" (yeah...really bad pun) in assuming that the new laptop / burning software also featured buffer under-run protection. I learned my lesson. Fortunately I still had the files on my computer and was able to produce another set of back-up discs to replace the ones which had the CRC errors.

So take precaution when burning discs of your critical image files. Verify that your images are all on the burned disc. I find the best way to do this is to open the finished disc and view ALL of the thumbnails. If there are any corrupt files, the thumbnails will not fully load (they'll look like they are halfway loaded with a portion of the image greyed out). You should also spot check a good number of image files by fully opening them to verify the files on the CD or DVD are good.

~DJW

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