Switch to DVD backup media from CD?

[Pan]

They can indeed.

It's very interesting to hear the contrasting views on DVD reliability.
It seems that taking all information into account, the end conclusion that
can be reached from all this is that while there is no reason not to
switch to DVD at this stage, caution is indicated on a rather grand scale.
It seems the best approach is to make multiple copies of everything burned
and to replace them with new copies every two or three years to ensure
nothing goes wrong. From time to time, all media should be checked
to ensure nothing untoward is happening to the data. None of the tasks
should really be too difficult since technology would of moved on to newer
format DVD drives by then and the media cost at the moment isn't too
significant. In addition, backup discs are used to restore data, so most
will get automatic checks by default when you are doing that.

My thanks to everybody who replied in this thread. Your help has been
invaluable.

Regards,

Pan

 

[Alexander Grigoriev]

It only means that RW has diferent decay factors. For example, it may be
more prone to humidity.

 

[Pan]

DVD-rot is corrosion of the aluminum reflective layer on early disks.
It doesn't cause "small circles overlapping the bottom-side of the
disk".

I'll confess that my first thoughts identified the problem as having a
mechanical cause. However, I posted pictures onto a newsgroup and
discussed the issue with people and I wasn't the only person that had
suffered this problem with this particular DVD set. In fact, one person
was able to radically narrow down the DVD set the disc came from.
Apparently the solvent on these discs are known to break-down after some
time, causing strange patterns to appear on the surface. Even the retailer
I brought it from didn't grumble in the slightest and replaced it free of
charge. It's also a bit suspicious that the only discs affected by this
issue were two from the same collection......

The person who hosted the image for me still has them online. Have a look
at http://www.colinjones.co.uk/images/dvd-damage.jpg

Given all the evidence, I'm putting it down to DVD-Rot for now. However,
I'll tell you one thing, I really, really hope your wrong and I'm right,
or there's a rogue DVD player in my house still in use......

And rather than replacing the disk, just polish them out--that's why
there's thick polycarbonate there.

I got it replaced free anyway, so there was no purpose in doing that. I
would of tried that if it had come down to it though.

Regards,

Pan

 

[Pan]

It only means that RW has diferent decay factors. For example, it may be
more prone to humidity.

So why did it surprise you that the discs have lasted so long with
excellent reliability? After all, I could live in a rainforest

Regards,

Pan

 

[Rod Speed]

I'll confess that my first thoughts identified the problem as having a
mechanical cause. However, I posted pictures onto a newsgroup and
discussed the issue with people and I wasn't the only person that had
suffered this problem with this particular DVD set. In fact, one person
was able to radically narrow down the DVD set the disc came from.
Apparently the solvent on these discs are known to break-down after some
time, causing strange patterns to appear on the surface. Even the retailer
I brought it from didn't grumble in the slightest and replaced it free of
charge. It's also a bit suspicious that the only discs affected by this
issue were two from the same collection......

The person who hosted the image for me still has them online.
Have a look at http://www.colinjones.co.uk/images/dvd-damage.jpg

Those circles dont look like 'solvent' effects to me.
The circles are FAR to regular to be something like
that. Its gotta be some sort of mechanical effect.

 

[Rod Speed]

It's very interesting to hear the contrasting views on DVD reliability.
It seems that taking all information into account, the end conclusion
that can be reached from all this is that while there is no reason not to
switch to DVD at this stage, caution is indicated on a rather grand scale.

Particularly with something as important as backup.

It seems the best approach is to make multiple copies of everything burned

On multiple media technology too. In other words say both R and RW

and to replace them with new copies every two
or three years to ensure nothing goes wrong.

Dunno, I think inspection at that rate makes more sense than
automatic copying. To catch DVDs going bad before all copys do,
so you can copy the still good copy before all copys have gone bad.

From time to time, all media should be checked to
ensure nothing untoward is happening to the data.

None of the tasks should really be too difficult since technology
would of moved on to newer format DVD drives by then

Dunno about that with 2-3 years. The progression from
CD to DVD has been over a much longer time than that.

and the media cost at the moment isn't too significant.

Yeah, not even worth considering in my opinion.

In addition, backup discs are used to restore data, so most
will get automatic checks by default when you are doing that.

Yep, thats what happens with applications particularly.

My thanks to everybody who replied in this
thread. Your help has been invaluable.

Thanks for the interesting discussion.

 

[Ron Reaugh]

Long term shelf storage and durability are two different issues. CDRW is
known to be a poor long term shelf storage media; CDRs are a different
matter. Durability is completely different from shelf life for offline
storage. One must not confuse the MTTF of a music CDR on a teens dash with
quiet shelf storage on a spindle or in a crystal case.

Filtering out format and/or drive compatibility issues has anyone ever
actually seen any signs of well stored and very infrequently mounted CDRs
going bad just with time(I haven't)? All the information I've been able to
find suggests that they last a very long time. The discussion is whether
CDRs last 15, 50 or 150 years to my understanding.

What's the truth about CDRs is a necessary precursor to this DVDR[/W]
discussion.

 

[chrisv]

Long term shelf storage and durability are two different issues. CDRW is
known to be a poor long term shelf storage media; CDRs are a different
matter. Durability is completely different from shelf life for offline
storage. One must not confuse the MTTF of a music CDR on a teens dash with
quiet shelf storage on a spindle or in a crystal case.

Filtering out format and/or drive compatibility issues has anyone ever
actually seen any signs of well stored and very infrequently mounted CDRs
going bad just with time(I haven't)? All the information I've been able to
find suggests that they last a very long time. The discussion is whether
CDRs last 15, 50 or 150 years to my understanding.

What's the truth about CDRs is a necessary precursor to this DVDR[/W]
discussion.

Clueless gibber.

 

[J. Clarke]

I'll confess that my first thoughts identified the problem as having a
mechanical cause. However, I posted pictures onto a newsgroup and
discussed the issue with people and I wasn't the only person that had
suffered this problem with this particular DVD set. In fact, one person
was able to radically narrow down the DVD set the disc came from.
Apparently the solvent on these discs are known to break-down after some
time, causing strange patterns to appear on the surface. Even the retailer
I brought it from didn't grumble in the slightest and replaced it free of
charge. It's also a bit suspicious that the only discs affected by this
issue were two from the same collection......

The person who hosted the image for me still has them online. Have a look
at http://www.colinjones.co.uk/images/dvd-damage.jpg

Given all the evidence, I'm putting it down to DVD-Rot for now. However,
I'll tell you one thing, I really, really hope your wrong and I'm right,
or there's a rogue DVD player in my house still in use......

Might be a manufacturing defect in the disk, but it looks like a different
problem from DVD-rot, which is described here

 

[Neil Maxwell]

Those circles dont look like 'solvent' effects to me.
The circles are FAR to regular to be something like
that. Its gotta be some sort of mechanical effect.

Yep, definitely mechanical.

They look like stress fractures to me. I don't know enough about
polycarbonate structure and DVD layer bonding to suggest why they'd be
so circular, but if I had to guess with no data, I'd say some
combination of chemical variation and thermal effect in their process
left the poly with a micro-crystalline structure that got past their
QA (which presumably has been updated now).

This could start fracturing under either rotational stresses or
thermal stresses caused by temperature differentials between the top
and bottom layers.

Was it only one side that showed this, or did both poly layers have
the same problem? Even then, it's possible the top and bottom poly
formulations have different specs, since optical specs are much more
important on the bottom layer.

If DVD-optical-grade poly is cheap and easy (and you'd think it is,
based on media prices), it's probably cheaper to use the same stuff
for both top and bottom layers, but they may run each batch through QA
tests and high-grade the bottom layer.

Fascinating...

 

[Neil Maxwell]

Filtering out format and/or drive compatibility issues has anyone ever
actually seen any signs of well stored and very infrequently mounted CDRs
going bad just with time(I haven't)? All the information I've been able to
find suggests that they last a very long time. The discussion is whether
CDRs last 15, 50 or 150 years to my understanding.

I have, as was discussed in other parts of the thread and various
other threads in the archives.

I've got multiple disks that were stored in cool, dark drawers in
jewel cases with no labels or inserts that are stone cold dead. Some
of these were written on quality blanks (by the standards of the time)
on a Plextor burner.

Anyone counting on a burned CDR lasting 15 years or more is in for an
unpleasant surprise, IMO, but we haven't been burning CDRs on a large
scale for that long yet, so the data set is incomplete.

Some people report no problems with disks written 8 or more years ago,
and I wish them the best. YMMV, as always.

 

[Rod Speed]

Yep, definitely mechanical.

They look like stress fractures to me.

Not to me, FAR too regular for that. Stress fractures arent.

Looks more like something stomped on the DVD, something round.

I don't know enough about polycarbonate structure and
DVD layer bonding to suggest why they'd be so circular,

Thats gotta be because they were done by
something that circular and that uniform in size.

but if I had to guess with no data, I'd say some combination
of chemical variation and thermal effect in their process
left the poly with a micro-crystalline structure that got past
their QA (which presumably has been updated now).

Cant see how anything like that could produce such uniform
sized perfect circles. Its gotta be due to something of that
shape stomping semi randomly on the DVD at some time.

This could start fracturing under either rotational stresses
or thermal stresses caused by temperature differentials
between the top and bottom layers.

That couldnt produce such identical sized circles.

Was it only one side that showed this, or did both poly layers
have the same problem? Even then, it's possible the top and
bottom poly formulations have different specs, since optical
specs are much more important on the bottom layer.

 

[Ron Reaugh]

I have, as was discussed in other parts of the thread and various
other threads in the archives.

Do you have any links or times/dates/titles/NGs to such discussions?

I've got multiple disks that were stored in cool, dark drawers in
jewel cases with no labels or inserts that are stone cold dead. Some
of these were written on quality blanks (by the standards of the time)
on a Plextor burner.

Your the first I've seen make such a claim.

The expert consensus is summarized(they last a damn long time but how long
is unclear yet) here:
http://www.itl.nist.gov/div895/carefordisc/CDandDVDCareandHandlingGuide.pdf

Anyone counting on a burned CDR lasting 15 years or more is in for an
unpleasant surprise, IMO, but we haven't been burning CDRs on a large
scale for that long yet, so the data set is incomplete.

Some people report no problems with disks written 8 or more years ago,

That would include me.

 

[Pan]

On multiple media technology too. In other words say both R and RW

Agreed, I forgot about that.

Dunno, I think inspection at that rate makes more sense than
automatic copying. To catch DVDs going bad before all copys do,
so you can copy the still good copy before all copys have gone bad.

Yep, I guess I can agree with that. But to be honest, having additional
copies of the media would be useful in any case, so if it's convenient to
do so, i.e if new technology was available, it would be worth it.

Dunno about that with 2-3 years. The progression from
CD to DVD has been over a much longer time than that.

Agreed, but if you look at the new DVD drives coming in next year
supporting 15gig DVD discs, then I think we can assume that the market is
going to move a bit faster this time.

Thanks for the interesting discussion.

It has. Thanks again.

 

[Pan]

Those circles dont look like 'solvent' effects to me.
The circles are FAR to regular to be something like
that. Its gotta be some sort of mechanical effect.

Actually, I think the opposite is true. Firstly, I know the DVD's were not
like this when I first had them. Secondly, I look after my CD/DVD's
extremely well. So I know that if the cause was indeed mechanical, it must
of happened in a drive during operation.

If I did, let me reveal further details about the discs. The disc shown in
the photo is the worst affected. The other one is much less affected, the
circle patterns are far less noticeable, but you can see that the effect
between the two is similar. In addition, the effect is much less
widespread, only visible on the outside part of the disc across one side.

If the damage was caused by a CD spinning in the drive, I suspect the
damage would be more evenly spaced. But it seems to be clustered in areas,
you might notice that even on the picture, areas of the disc appear
completely untouched, while others are completely marked very heavily with
more than one overlapped circle. In addition, if the damage had been
caused by something in the drive, wouldn't it of been extremely noisy when
it occurred? I'm sure I would of noticed that.

Given all the other information I provided regarding the problem
identification, I find it hard to believe that all that data is just a
coincidence and the real problem is a simple drive failure. I don't know
if the problem is DVD-Rot, but it seems unlikely to be a drive failure
from what I can tell at the moment.

Regards,

Pan

 

[Pan]

Yep, definitely mechanical.

They look like stress fractures to me. I don't know enough about
polycarbonate structure and DVD layer bonding to suggest why they'd be
so circular, but if I had to guess with no data, I'd say some
combination of chemical variation and thermal effect in their process
left the poly with a micro-crystalline structure that got past their
QA (which presumably has been updated now).

It seems interesting to me that a lot of the discs reported to suffer
problems are produced by Warner Bros....

This could start fracturing under either rotational stresses or
thermal stresses caused by temperature differentials between the top
and bottom layers.

Was it only one side that showed this, or did both poly layers have
the same problem? Even then, it's possible the top and bottom poly
formulations have different specs, since optical specs are much more
important on the bottom layer.

Just one side had marks like that. The other side was misted up really
badly. I found it interesting because it had clear patches in the mist
that looked almost normal. That stinks itself of some kind of surface
breakdown.

Fascinating...

It wasn't fascinating for me. It was horrifying I had to see this
damage first-hand without warning.

Regards,

Pan

 

[Pan]

Might be a manufacturing defect in the disk, but it looks like a different
problem from DVD-rot, which is described here
<http://www.andraste.org/discfault/discfault.htm>.

DVD-rot is just my umbrella term for disc manufacturing problem. I have no
idea what specific problem it may have. I find it interesting that Warner
Bros discs seem to appear prominently in problem examples though.

Regards,

Pan

 

[Rod Speed]

Rod Speed wrote

Actually, I think the opposite is true.

I'm not convinced with those circles. FAR too regular diameter wise.

Firstly, I know the DVD's were not like this when I first had them.
OK.

Secondly, I look after my CD/DVD's extremely well.
OK.

So I know that if the cause was indeed mechanical,
it must of happened in a drive during operation.

Yeah, thats a real possibility, thats the head hitting the surface.

If I did, let me reveal further details about the discs. The disc shown
in the photo is the worst affected. The other one is much less affected,
the circle patterns are far less noticeable, but you can see that the
effect between the two is similar. In addition, the effect is much less
widespread, only visible on the outside part of the disc across one side.

That fits the head possibility, its only on one side.

If the damage was caused by a CD spinning in the drive, I suspect
the damage would be more evenly spaced. But it seems to be
clustered in areas, you might notice that even on the picture,
areas of the disc appear completely untouched, while others are
completely marked very heavily with more than one overlapped circle.

But if the disc didnt get grabbed by the grabber properly...

In addition, if the damage had been caused by something in
the drive, wouldn't it of been extremely noisy when it occurred?

Not necessarily.

I'm sure I would of noticed that.

If you had been at the PC when it happened, anyway.

Given all the other information I provided regarding the problem
identification, I find it hard to believe that all that data is just a
coincidence and the real problem is a simple drive failure.
I don't know if the problem is DVD-Rot, but it seems unlikely
to be a drive failure from what I can tell at the moment.

On the other had its very hard to see how those identical
diameter circles could be produced other than mechanically.

 

[Mike Redrobe]

On Thu, 09 Jun 2005 20:47:14 -0400, J. Clarke wrote:

DVD-rot is just my umbrella term for disc manufacturing problem. I
have no idea what specific problem it may have.

I find it interesting that Warner Bros discs seem to appear prominently
in problem examples though.

Maybe they sell more DVDs ? Or they are played most often ?

 

[Pan]

Maybe they sell more DVDs ? Or they are played most often ?

I can't say much to that But I suspect they just aren't made as well

Regards,

Pan