clipka wrote:
> Okay, so I burned that CD-ROM image four times now 

If it's a Linux image, it probably has a top-level menu option to check the 
disk. This (I believe) checksums each file individually, so you'll catch 
problems like the wrong files or missing files or something, even if the 
disk is burned correctly.  I've had that happen once - good burn of a bad 
Linux, for some reason.

-- 
   Darren New, San Diego CA, USA (PST)
   I ordered stamps from Zazzle that read "Place Stamp Here".

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clipka wrote:
> 
> The only common things between the attempts (aside from the image in
> question of course, which is ok according to md5 checksum) are (a) the
> CD/DVD writer brand (both are LG, maybe even same model), and (b) the
> CD-R media brand and batch.
> 

It is possible and I've *once* seen it happen, that the file is
corrupted and still gives the correct MD5 checksum. If possible, try
also another checksums (SHA-1 for example).

-Aero

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Fredrik Eriksson schrieb:

> Burn speed can have quite an impact on the stability of the burned data. 
> Never burn at 56x; personally I would not go over 16x unless I planned 
> to only use the disc once. However, modern discs and drives generally do 
> not fare well with the lowest speeds either. Try to find a middle 
> ground, like 8x or 16x depending on the burner; you do not want to push 
> the burner to its limits either.

16x is what I actually started with.

> It is not unheard of to get a few bad ones in a row; it has happened to 
> me as well. A small hiccup in the manufacturing process probably.

How many would that be, usually? Is it worth trying the remaining ~25 in 
  the box?

(Then again, maybe I should just try the one at the bottom...)

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TC schrieb:
> How do you know burning the image did not work?

Multiple symptoms:

* Verify of CDBurnerXP warned that verify failed in both attempts.

* Copying one of the CDs burned with CDBurnerXP to hard disk failed.

* Booting another computer from the CD (an openSUSE installation image) 
worked, but the inbuilt "check installation medium" (or whatever it's 
called) ran on a CRC error in one case, and some other error in another 
case.


> Or did you just try to use the burned DVD and it did not work? Then maybe 
> the original image-file contains crap. Had this once, burned an image file, 
> tried to open it, it did not work. Did it again, still did not work. Then 
> looked at the image file using DAEMON tools and found that the data mastered 
> in the DVD-image was invalid - the image file was OK, though.

Ran an md5 check on the image, and it was ok. Being an official openSUSE 
11.2 installer image, I guess Jim will confirm that we can rule out bad 
mastering :-)


> Apart from this, if store CD/DVD improperly you can damage them. Never 
> expose them to direct sunlight for any long period of time, never store them 
> where it is too hot or too dusty.

Hm, now that you mention it... I'm not sure, I /might/ have kept them 
for a while where they'd get a beam of direct sunlight for a few minutes 
on a sunny day. Not sure though.


> Be careful where you put them - I once stacked some CD-R's one on the other. 
> After a few years the cd-label marker I had used to label the CD-R diffused 
> from the up-side of the bottom CD surface into the underside of the CD on 
> top. I was lucky and the data was still readable, but this was a valuable 
> lesson of "how NOT to do it". 

They're still in the original cakebox; you'd expect that to be somehow 
suitable for storage of CD-Rs ;-)

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On Mon, 16 Nov 2009 20:48:20 +0100, clipka <ano### [at] anonymousorg> wrote:
>
>> It is not unheard of to get a few bad ones in a row; it has happened to  
>> me as well. A small hiccup in the manufacturing process probably.
>
> How many would that be, usually? Is it worth trying the remaining ~25 in  
> the box?

I have personally seen only 2-3 bad ones in a row, but since it  
essentially entirely random, there are two basic approaches: Keep going  
through the pile until one works, or assume it was a bad batch and throw  
away the lot.

Also consider that perhaps the burner just does not get along well with  
these discs; sometimes a firmware upgrade can help with that. Keep in mind  
that buying the same brand/label that you used before does not guarantee  
that the discs are the same.

Additionally, as TC pointed out, make sure the image itself is not bad.



-- 
FE

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Eero Ahonen schrieb:

> It is possible and I've *once* seen it happen, that the file is
> corrupted and still gives the correct MD5 checksum. If possible, try
> also another checksums (SHA-1 for example).

You've seen an MD5 checksum collision? Gee! You should be playing 
lottery ;-)

It also turned out later that the installer medium test failed with 
different error messages for different CD-Rs (yet same image); on the 
other hand, it did /not/ fail with the USB stick I later extracted the 
files to.

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clipka wrote:
> 
> You've seen an MD5 checksum collision? Gee! You should be playing
> lottery ;-)

A friend of mine hit it. Yes, it's extremely rare, but it's still possible.

And yes, I am playing lottery. Actually, on this year I'm still 6e oslt
on profit ;-).

> It also turned out later that the installer medium test failed with
> different error messages for different CD-Rs (yet same image); on the
> other hand, it did /not/ fail with the USB stick I later extracted the
> files to.

Ah, then the image should work. Just use the USB-stick? :-)

-Aero

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Eero Ahonen schrieb:

> Ah, then the image should work. Just use the USB-stick? :-)

Well, of course, that's what I did in the end.

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