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Durablity????

PostPosted: Fri Sep 10, 2004 11:53 am
by quired
My friend tell me that CD or DVD can only last for around 3 years. Is he right?

PostPosted: Fri Sep 10, 2004 12:04 pm
by Ian
It depends on a number of things:

1. quality of the media
2. how the discs are handled
3. how they're stored - temperature, humidity, light, etc

For example, if you archive your data to some high quality media and store them away in a saftey deposit box, its more than likely, you'll be able to read it 10-20 years from now. However, if you burn it to lower quality discs and let them lay around in say your car, they're not going to last nearly as long.

PostPosted: Sat Sep 11, 2004 3:14 pm
by avsgenie
I've only just got a DVD drive and have been backing up my CD data collection. 71 CD's, the earliest dating from January 1997 (burnt on a Plasmon x2 drive). All read without a hitch. These are copies just knocking around in jewel cases in my room. I do also have 2 spares of each in the loft - dark but not always terribly cool.

Other than the most recent, all had gold reflective layers - don't know whether this will make a difference in the long run, and all are either TDK, Verbatim, or Kodak.

Logically, as data densities increase, reliability must decrease, but DVD's do include a greater percentage of error correction bits than CD's. However, the disks only have to last as long as it takes to develop the next higher capacity format. I'm sure blue ray won't be the last, but I guess there are physical limitations.

Given the rapid expansion in digital photography, I'm sure that some company will eventually hit upon the marketing strategy of longevity as an issue. I have to say, I still shoot film, and digitise with a scanner.

PostPosted: Sat Sep 11, 2004 6:48 pm
by alexnoe
Princo discs can easily fail after 2 months, whereas the CDs i've burned 1997/98 are still totally ok (TDK, dark blue stuff)

PostPosted: Sun Sep 12, 2004 2:04 am
by pranav81
I believe that the condition of the discs mainly depend on the storage conditions.And the quality of the media matters a lot.


::Pranav::

PostPosted: Sun Sep 12, 2004 3:59 am
by happyperoil
ty cdr's by tdk i burned 5/6 year ago now are still readable.
many cmc disks by memorex and some by verbatim went to trash after 2/3 years. also traxdata disks are not reliable

PostPosted: Mon Sep 13, 2004 11:58 am
by Halc
Ian pretty much nailed it in his first post.

However, here's my elaborated take on the issue:

The quality that determines the the longevity of an optical disc:

1. optical disc quality (bonding quality, refletive layer material, dye layer material, label side materials, general QA of batch variability)

2. burner quality (low level) and compatibility with the burned media (firmware, burning strategy, optics, etc)

3. burning speed (i.e. not always the lowest speed, but right speed with the right strategy for the right media)

The above three pretty much decide the starting point for media longevity (i.e. low level burned disc characteristics, error counts and physical/chemical stability).

If any of the first three is seriously compromised you may end up with a disc that is not even worth archiving in the first place.

Then on to the archival

4. Archival, which includes, but is not limited to: protection from:

- noxious gases (sulphur compounds, ozone and general air pollutants)
- acidity (from various plasticicers used in jewel cases and cd sleeved folders that are not of archival quality)
- solvents (from various plastic manufacturing processes, sometimes wrongly chosen cd markers and even human skin contact, because grease can be a solvent too)
- radiation: namely infrared (heat) and UV radiation, but just plain "visible spectrum light" as well
- temperature (both absolute high/low temps and temperature changes): ideal is between 20-25 and no big changes
- humidity: relative humidity should be controlled and should not change quickly
- physical stress (bending, vertical uniform pressure, straching, etc)
- archival materials/storage containers used (which may contain hazards in addition to the above)

The above pretty much determines how long a disc can survive, until it starts to oxidizate, delaminate, loose it's dye stability or otherwise fail.

5. Handling determines how well the disc can survive, once it is taken from archival to intermediate use again. This includes handling the discs (fingerprints, bending, writing, scratching, read spinning speeds, labelling, etc).

6. Selection of readers determines the disc longevity in practical terms as well. If you have a pristine disc that has great low level values and intact data, but absolutely no-good readers then the data on the disc is pretty much irrelevant.

So, a good archival also takes into account the fact that a sufficient reader (physical level device) along with logical level file format support is still available at the time when the media needs to be taken from archives and read back again.

That's about it in short.

The longer list would include recommendations and guidelines, which can be gathered from NIST, OSTA and archival specialist publications.

Now as to the question how many years will dvd discs last?

It all depends on the above, but using the best discs, burners, storage and processes, they could ideally last for decades.

However at this point, nothing is sure, except the fact that dvds I burned more than 3 years ago are still functioning without any problems (high quality burners/high quality media/proper storage).

cheers,
halc

PS Many people are not aware of this, but a lot of the el-cheapo jewel cases are in fact worse for archival of cd/dvd discs than just putting them in a decent archival sleeved folder or even paper bags. Why? Because the plasticicers used with many ABS compound jewel cases cause the acidity inside the case to rise and start the slow but steady delamination/oxidisation of the disc.

PostPosted: Mon Sep 13, 2004 10:15 pm
by Phoenix '97
alexnoe wrote:Princo discs can easily fail after 2 months, whereas the CDs i've burned 1997/98 are still totally ok (TDK, dark blue stuff)


I have quite a few Princo 1x and 2x DVD-Rs I burnt over a year and a half ago that are still quite readable.

PostPosted: Mon Sep 13, 2004 10:35 pm
by dodecahedron
Phoenix '97 wrote:
alexnoe wrote:Princo discs can easily fail after 2 months, whereas the CDs i've burned 1997/98 are still totally ok (TDK, dark blue stuff)


I have quite a few Princo 1x and 2x DVD-Rs I burnt over a year and a half ago that are still quite readable.

WOW! astounding!