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crahak, on Jun 20 2006, 04:24 PM, said:
The magnetic "data" on the platters is very very stable - you could leave it alone for MANY years with no problem.
That's a common mistake. I have CD-R, first generation (when CD burners were at least as costly as BD burners now) that proven to be more robust than HD bought within the same period (it were old HD... less than 500 MB). Noticeable thing is that both CD-R and HD were "low-cost" ones !
I presume that this year's HDs are more robust ; but optical discs are also.
crahak, on Jun 20 2006, 04:24 PM, said:
You're misunderstanding. We're not talking about CRC-like error checking for transmission, or to verify if data blocks were valid - DVDs use those error correction bits to fix stuff that wasn't recorded properly (they even measure things like this i.e. BEL and such). All discs have loads of PI errors and some PO errors - no burn is ever "perfect", and cheap discs are quite bad (increasing burning speed only makes things worse - and who wants to burn slow?) HDs don't rely on that type of "error correction".
Imperfect burns, combined with dyes that change over time (especially discs using organic dye - most discs do), and all the previously mentionned factors (temp, humidity, etc), imperfect manufacturing (very common - improper sealing, imperfections in plastic, etc), and some disc aging problems (like pin holes in some discs, plastic becoming cloudy on others, oxydization, etc), and with everyday wear (scatches and dust)...
Imperfect burns, combined with dyes that change over time (especially discs using organic dye - most discs do), and all the previously mentionned factors (temp, humidity, etc), imperfect manufacturing (very common - improper sealing, imperfections in plastic, etc), and some disc aging problems (like pin holes in some discs, plastic becoming cloudy on others, oxydization, etc), and with everyday wear (scatches and dust)...
Who wants to burn slow ? I burn slow and leave comp away. Especially for something like a backup !
Again, you're making strange comparisons... neglicting that HD heads read/writes operations are far more complex than optical read/write ! Imagine that each time the HD needs to read a bit, it must re-write it after (including error correction bits) ! It involves MUCH more operations than for an optical disc, thus dramatically increasing the risk of error (this is meaning that checking if a HD has errors can create errors, whereas checking if a CD has errors won't).
Indeed, no optical burn is ever perfect. Same thing for magnetic write.
Indeed, optical drives have lots of error correction features. But no more than HD.
You're talking a lot about disc manipulation : this has nothing to do with its reliability ! Can you imagine manipulating a magnetic plate by hand ? No ? So keep the disc in its box, and you avoid half of these problems. Use a drive that accept optical cartdriges, and you avoid half of the rest. Store you disc in an appropriate place, and you avoid half of the rest.
What remains ? well... you'll need a lot of imagination to find, and even more malchance to do !
crahak, on Jun 20 2006, 04:24 PM, said:
Plus, magnetic storage, as the name suggest, is subject to magnetic sensivity
Not so. The drive's in a metal box (faraday cage).
Not so. The drive's in a metal box (faraday cage).
Here comes an enormous misconception !
Imagine that a car, a train, an elevator are faraday cages. But you can use your cell phone when you're into. Easy for a car or a train, a bit tricky for mosts elevators.
Nearly no faraday cage is perfect (never "took electricity" when trying to open your car in a windy day ?).
http://en.wikipedia....ki/Faraday_cage (read the part about microwave oven, it's the more interesting in this case)
Obviously, the HD box is robust. But if the disk stay (like backup disks usually do), errors can occur. (did you noticed that most backup software adds software error correction checks ?)
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