Pressed vs burned DVD for best longevity & error-rate

[raffaella]

I have some precious home movies which I have backed up as identical MPEG files on a pair of eternal hard drives.

But I would like to also copy them to DVD. Then I recalled a claim someone made that movies issued on commercial
DVDs have longer life spans because DVD studios "press" the DVDs rather than use computer DVD 'burner" drives.

Is this true? If so, than assuming one uses reasonably reliable (Verbatim? Sony?) blank dual-layered DL +/- blank
media and burns the disk at a slow (more error free?) speed, what DVD lifespan and error-rate could one expect,
compared to a pressed copy?

[chase]

While you're waiting for an expert response, you could try reading here: http://dvddemystified.com/dvdfaq.html#3.12 (and following the links given?).

[Southae]

Hi, Folks!

My info. is based on what's been learned from the National Archives in their Virginia facility, along with independent testing. It turns out digital media storage methods all have unrecoverable errors which occur within 3 to 5 years of their creation. This applies to unrefreshed hard drives, CD and DVD R's, and tape. The layered medium used in DVD & CD-R's deteriorates over time, and if the hermetic seal is damaged on these discs, they then suffer what's referred to as "rot" as the medium exposed to air oxidizes, making them unplayable.

Both CD-R and DVD-R discs are generally optimized for various burn speeds. 1x burns may not transfer the data as accurately as 8x for CD's. As I understand it, there are concerns with bit rates, rotational speeds, media response, flatness of the discs during burning, and "jitter"; all of which determine the optimal burn rates for this type of media (and also lead to failure mechanisms too!).

Yes, the commercial releases are actually "pressed" from glass pit masters, and the resultant foil coating on the plastic discs is then hermetically sealed against potential damage. As long as this seal stays intact, this media will generally last considerably longer than laser "burned" media.

If you are truly looking to preserve digital media for a long time, the current suggested approach is to make two hard drive copies of the media. Store them in different, temperature and humidity controlled environs (the National Archive uses a chilly 50-degrees Fahrenheit, 10-degrees Celsius), and "refresh" this data annually if not sooner after checking both drives for errors. The "refresh" process essentially consists of re-copying data to a third drive to be "rotated" with one of the other two on a periodic basis. Further, make sure none of the hard drives are from the same production or manufacturing lot. Tolerances are so tight on the manufacturing of hard drives these days, that drives from the same lot tend to fail within a few 100 hours of each other, assuming parallel run times.

If you're familiar with IT type backup systems, this is essentially what they do to backup critical corporate database drives. Its not bullet proof, but will preserve the data from not only drive failures, but if duplicate drives are stored in separate locations, this can prevent loss through fire, flood, or other catastrophes.

The only issue with this method, is that the original playback equipment must sometimes be maintained too. MFM drives are now antiques, and EIDE and SATA's may well succumb to Solid State Drives in the not too distant future... yet, there has to be a way to playback this info.

B.T.W. I'm storing most of my recent digital data in at least two duplicate external drives for archival purposes. I have a number of tapes however, for which I haven't (or cannot) duplicate without some loss (many are analog masters), and these are stored in a temperature and humidity controlled environment, close to what the National Archive is using (although I don't refrigerate them, just keep them at or below 50% relative humidity at around 70-degrees Fahrenheit, 20-degrees Celsius).

Hope this helps!
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[Neil Wilkes]

I could not agree more with everything Southae just wrote.
Written discs cannot be trusted - period - and HDD will fail if not spun up regularly too.
External HDD are more prone to this than internals, especially FireWire as the controller chips can burn out & take either your mobo (if the main controller is mobo based) or your expansion card down with it - this happened to me.
The spindles can freeze too, if not spun up regularly.
Someone once lost an entire tour recording because of this.
Frozen spindles can be unfrozen if you are feeling up for a trick though.....
Make the thing airtight, then reseal it & make that airtight too.
Slap it in a deep freeze for 24 hours, then defrost, unpack & try to spin up.
If it does - get the data off, fast (similar to baking old tapes, really, inasmuch as it is a temporary fix only)
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