An
article was published in the New York Times today on the benefits of backing up your data in case of emergency. It focused on the losses by victims of Hurricane Katrina, namely one couple – Mike and Janet England. The article, for the most part, was intended to reach out to the average computer user who, in most cases, does not back up his or her data (at least not frequently enough). It recommended a large variety of different backup methods from readily-available CD/DVD systems, to now less-common tape backup systems, to in-home network fileservers (though I don't really see how a fileserver would help you against disasters like Katrina), to the more expensive high-capacity remote storage (i.e. big web storage).
Disclaimer: this is somewhat of a technical rant, though I find it important to say.
I feel this is a very important topic to cover, as I see it all the time when I am home (I work at an Apple Store where, upon hearing we needed to reformat the machine, the general user gives the response "BUT THIS IS AN APPLE!"). However, I disagree with some of the recommendations given in the article. The author, Kate Murphy, first proposes CD/DVD storage as an inexpensive solution. She states, however, that they are "good choices if you only want to save a lot of documents." As I believe many of us know here on Delphi, this is simply not true. With DVD storage you can store most, if not all, of the files you will ever need to save on a few DVDs, especially if you have a dual-layer burner capable of holding close to 9GB on one disc.
She goes on to give an example of a user who, having "a modest music library of 50 songs, a dozen movies, five years of tax returns, several sets of vacation pictures — plus a lot of documents," according to her, would have a need for backup capacity of "more than 100 gigabytes of data." I don't know where exactly she got this estimate but it seems
very far-fetched to me. I'll do a quick back-of-the-envelope (with a few average sizes - please correct me if I'm wrong on any of them):
(50 songs)(4MB/song)+(12 movies)(650MB/movie)+(5 sets)(50 pictures)(100KB/picture)+(500 documents)(50KB/document)=8.1GB (approx.)
This amount of data could be stored on
1 dual-layer DVD! Think of what you could store on 2!
Now add to this the fact that the average user who has "a modest" 50 songs on his or her computer is most likely
not going to have the knowledge to download 12 compressed movies (let alone uncompressed..). This certainly does not constitute a need for an external hard drive storage system that would be both more difficult to carry in an emergency, and more susceptible to water damage in the case of a flood.
Murphy states as one of the downfalls of optical disc storage the fact that the discs "can be easily scratched and warped." While this is true, this kind of physical damage can be avoided by using a protective case for the disc. Not only that, optical data storage is a very resilient system.
First of all, the refraction of the laser due to the polycarbonate layer allows for a good deal of scratching before damage is done. One should note that the CD's data layer is near the top of the disc and therefore scratches on the top actually do [/i]a lot[/i] more damage than those on the bottom which are normally attributed to skipping discs – never write on a CD with anything other than felt-tipped marker. The DVD's data is stationed in the middle of the disc which decreases the effect of the refraction on scratching, but it is still very much a present quality.
Second, the data on a CD is interleaved using a CIRC –
Cross-Interleaved Reed-Solomon Code – scheme as part of error correction (I was unable to find a good image to help explain CIRC so please post one if you can find it). This means that data is essentially scattered all around the disc. Because of this, a scratch or error of some sort in a single location will only hurt a small chunk of a frame of music, rather than risking the whole frame. The damaged data can often be revived by using the second (RC - Reed-Solomon Code) part to reconstruct the original signal through a system of parity and modulo-2 arithmetic. Because of the CIRC encoding on a CD a person could theoretically (and yes, I did do this) drill up to an 1/8" hole in a disc before experiencing noticeable errors in playback. Again, note that this flexibility is lessened in the case of a DVD, but is not non-existent.
In all, while it is very important to educate the average computer user as to the many dangers lurking out there and the importance of redundant storage of data, it is also important to give them the true facts. CD/DVD backup systems are very inexpensive, more portable, more-readily cross-platform, and
less susceptible to most damage than hard-disk based systems. I would certainly recommend optical storage to the average user before a decidedly more expensive, and more fragile disk drive.
Comments?