Archiving software CDs under Win98 Pitfalls and challenges
Posted 13 February 2010 - 09:27 AM
1) Archiving software CDs with out-of-spec filenames
A software CD, burnt around 1998, contained directory names which were not legal under ISO 9660. See http://en.wikipedia.org/wiki/ISO_9660 I assume it contained 3 subdirectories with dots in their directory names: "5.5DDocs", "5.6Addendum" and "5.6Tutorial". Unfortunately I cannot check the CD anymore, since the CD has gone bad in the meantime, with silvery flakes peeling off the CD.
Before the CD went bad I had made under Win98 an Ok file copy with Windows Explorer (and also with Unstoppable Copier) to a USB HDD of all files and directories on the CD.
When I looked under Win98SE at these 3 subdirectories on the USB HDD they had the long file names "5 ~1.5dd", "5 ~1.6ad" and "5 ~1.6tu" (each with 4 embedded spaces, not correctly displayed here, and the long file name and the DOS file name were identical). Neither WinME ScanDisk nor standalone Norton Disk Doctor 2004 complained under Win98SE about the long file names.
When I looked under WinXP SP2 at these 3 subdirectories on the USB HDD they had different long file names: "5.5DDocs", "5.6Addendum" and "5.6Tutorial".
The only explanation I can think of why Win98 and WinXP assign different long names to the same directories is that when Win98SE stored an out-of-spec filename on the USB HDD, it somehow marked the filename as bad, and subsequently used the DOS name as LFN. In any case Win98 must have stored on the USB HDD the out-of-spec directory name of the CD, since WinXP reads it from the USB HDD.
I came across this problem when I made a binary compary with Beyond Compare under WinXP. I compared under WinXP the file-copy backup on the USB HDD against a mounted .iso image created under Win98 of the files on the USB HDD: they did NOT match. WinXP read the directory names on the USB HDD as "5.5DDocs" and the corresponding directory name in the mounted .iso (created under Win98) as "5 ~1.5dd".
The assigning by Win98 and WinXP of different long names to the same folders has 2 major implications:
1) Software backed up under Win98, from a CD with out-of-spec long names, into a .iso (or also as .rar, etc.) or even as a Windows Explorer file-copy will NOT work. A program looking for "5.5DDocs" will not look for "5 ~1.5dd"
2) Because of this out-of-spec problem, backup copies of CDs, made under Win98 may not be reliable. It may be preferrable to make backup copies of CDs under WinXP instead of under Win98.
This 12-year-old CD may be an example to explain the somehat cryptic text in the Wikipedia article: "... most operating systems which can read ISO 9660 file systems have no problem with out-of-spec names. However, the names could appear wrong to the user." http://en.wikipedia.org/wiki/ISO_9660
Is there some software which checks whether a CD (or HDD) contains out-of-spec file or directory names?
Posted 13 February 2010 - 03:00 PM
So the phenomenon of these 3 directories "5.5DDocs", "5.6Addendum" and "5.6Tutorial" on my backup HDD being assigned different names by Win98 and WinXP is probably NOT caused just by a dot in the directory name.
Maybe it is caused by the embedded blanks in the DOS directory names "5 ~1.5dd", "5 ~1.6ad" and "5 ~1.6tu". I guess the embedded blanks were automatically created as fillers because the first part of the directory name consists of a single character "5", and the suffix exceeds 3 characters.
I don't know how the embedded blanks got into DOS directory names on my backup HDD. When, for example, I create under Win98 the folder "1.junk", Win98 assigns it the DOS folder name "1~1.JUN", without embedded blanks. Maybe it has something to do with ISO Level 1 (8.3 characters), it can't be coincidence that in each of the 3 directory names 4 blanks were embedded, giving a total length of 8 characters to the first part of each directory name.
Am I missing a MS bug fix on my Win98 computer? The whole problem looks like a MS bug, which was fixed under WinXP.
This post has been edited by Multibooter: 13 February 2010 - 03:24 PM
Posted 14 February 2010 - 04:51 AM
and/or a GUI for them:
You don't need to actually mount a .iso and use Beyond Compare or similar utilities, just create an compare the MD5 hashes of them.
Also, slightly off topic, but related:
This is "the real thing" (though you won't like it's price):
"Poor man's" version:
Posted 15 February 2010 - 03:46 AM
And speaking of XML output , and JFYI:
be AWARE of the (hopefully false) positive
Posted 15 May 2012 - 01:52 PM
Burnt CDs tend to have a life span of around 3-7 years, although I still have a couple of good CDs burnt around 15 years ago.
How to identify bad CDs/DVDs
A CD/DVD can be checked for bad sectors with ImgBurn by creating an image file from the CD. If no message like "Uncorrectable Error" is displayed, the CD/DVD is Ok and contains no bad sectors. ImgBurn also displays which file is affected by the specific bad sector.
ClonyXXL v188.8.131.52 , a copy protection scanner, has a bad sector scanner and could be useful to check whether a CD with bad sectors is copy-protected or not. Copy protection schemes often use intentionally bad sectors, and it would be useless to just wash or buff such a CD/DVD or read it in many times, bad sectors were put there for a purpose. ClonyXXL v184.108.40.206 can access CDs in an external USB enclosure under Win98SE, but not under WinXP. ClonyXXL v220.127.116.11 cannot check DVDs, only CDs. ClonyXXL helps to identify those CDs with bad sectors which in some jurisdictions should not be archived.
ImgBurn does not give a warning when the CD/DVD has bad sectors created intentionally for a copy-protection scheme, but displays normal messages like:
"Failed to Read Sector xxxx - Reason: L-EC Uncorrectable Error
Sector xxxx maps to File: \Lock\Lock.dat" (as a hypothetical example, the file name of the first bad sector could give a clue)
"I/O Error! .... Device: .... Interpretation: .... CDB Interpretation: Read CD - Sector xxx ... Sense Area Interpretation: L-EC Uncorrectable Error"
How to Repair a bad software CD/DVD (non-bootable, no copy-protection):
Step 1: Decide whether it is really worth the expense and effort to recover/repair a particular CD/DVD. Recovering/repairing bad CDs/DVDs can be VERY time-consuming. If a copy-protected software CD goes bad, an attempt at recovery may probably not be worth while.
The recovery of one really bad CD took me about 2-3 days, and I took it as an enlightening experiment. I was very lucky then that I had found good replacement files for all unrecoverable files (see Step 12), otherwise the whole recovery effort would have been in vain. When you embark on recovering/repairing a bad CD/DVD, you don't know the outcome. It may well be that the bad CD/DVD can never be repaired.
Step 2: Get your tool box together, like:
a) at least 3 CD/DVD/blu-ray burners which are very good readers in general
b ) ImgBurn v18.104.22.168
c) Unstoppable Copier v5.2 (WinXP) or v3.56 (Win98, does NOT copy zero-size directories)
d) an Aleratec DVD/CD Disc Repair Plus, model 240131
e) Beyond Compare v2.5.3 and the Hex Viewer plugin
f) UltraISO v22.214.171.12450
g) ClonyXXL v126.96.36.199
h) 7-Zip v9.20
i) 20GB of free space on a HDD for repairing CDs, 100GB for repairing DVDs
I have in my toolbox 5 different burners which are excellent readers. One reader may be able to read some sectors which another reader can't., maybe because of different alignments, maybe because of different hardware/firmware capabilities. It's a matter of trial and error, and collectively these good readers can recover a lot of stuff on bad CDs/DVDs.
Copying the content of a bad CD several times, e.g. with Unstoppable Copier or Beyond Compare, with the same burner may result in different sets of good recovered files. Reading a bad CD/DVD by sector, i.e. by creating a .iso file, has somehow produced more good files than reading a bad CD by file (as with Unstoppable Copier), no idea why.
I have kept a really bad CD as a tool to test the reading ability of burners. Somehow blu-ray burners and burners which can read/write Mount Rainier tend to be good readers, maybe because they have a particularly good error correction to compensate for the many errors on blu-ray and CD-RW media. One good reader I obtained by chance from an old PC, which a friend wanted to dispose of. After looking over his old PC I kept a couple of components, including the burner, and then took the remainder together with other stuff to a recycling drop-off. The reading ability of a good reader may deteriorate quickly after reading for many hours over the same bad sectors on a bad CD/DVD.
One reader may be good for +DVD media, another for -DVD media, it's a matter of testing. I have my good PATA and SATA readers in external USB enclosures, so they can be hooked up easily to any of my computers. On my list of projects I still have an old SCSI burner, which I would like to put into an external USB enclosure, any ideas are appreciated.
Step 3: the bad CD/DVD is washed with tap water and a mild dishwashing liquid, as used when washing dishes by hand, plus a good rinse.
Step 4: the bad CD/DVD is read in by sector (e.g. by UltraISO -> Tools -> Make CD/DVD Image, or by ImgBurn ->Create image file from disc), creating a pre-buffing iso image, with zeroes instead of bad sectors. If you use ImgBurn, and ImgBurn does not display an error message about a bad sector, then washing the CD/DVD was enough, and BINGO, you're done.
It is better to use in this step ImgBurn, rather than UltraISO. because ImgBurn creates a log file/error report, which allows to deduce that files not listed as having bad sectors, were read Ok. The log/error report by ImgBurn should be saved for later reference and analysis. UltraISO does not have a detailed log, but is easier to use, with fewer options and settings where one could make a mistake.
CloneCD v5.211, for example, is not useful for this step. CloneCD v5.211, when it encounters a bad sector during the creation of a .iso apparently tries to replicate the bad sector in the file mapped to the bad sector. As a results, when a file containing a bad sector is accessed on a mounted .ccd, e. g. with Windows Explorer under WinXP for a file copy, you get the error message: "Error Copying File or Folder. Cannot copy xxxx: Cannot read from the source file or disk".
MagicISO v5.5.0281 seems to fill a whole file with zeroes if only one of its sectors is bad, so it's not useful in this Step either. ImgBurn v188.8.131.52 and UltraISO v184.108.40.20650, on the other hand, replace just the bad sector area in the file with zeroes.
One interesting difference between the various iso programs is how they handle bad sectors.
Step 5: the bad CD/DVD is read several times by file by Unstoppable Copier, with various good readers, creating several sets of good files
Unstoppable Copier must have the setting "Auto Skip Damaged Files" selected, also "Include Sub Folders"and "Copy Empty Folders". I obtained the best results when "Set Maximum Retries" had the value 20 (possible range: 0 to 99). Beyond Compare could also be used to create the various sets of good files, but Beyond Compare does not display the number of Skipped Files as an easy single number. The reader which creates the set of good files with the most files in it, is the reader which can handle this specific bad CD/DVD best.
Step 6: the bad CD/DVD is buffed 5-10 times with the Aleratec DVD/CD Disc Repair Plus machine, removing a thin layer of plastic from the CD/DVD. The resulting CD/DVD is basically a different bad CD/DVD, with some previously bad sectors/files perhaps readable.
Step 7: try to create an image of the bad buffed CD/DVD with ImgBurn with the best reader for this CD, as identified in Step 5, creating a post-buffing iso image. There may be a chance that ImgBurn does not display an error message about a bad sector. If so, you are lucky, BINGO, a good .iso image was created, and you may proceed to step 15.
Step 8: the bad buffed CD/DVD is read several times by file by Unstoppable Copier, with various good readers, creating even more sets of good files.
Step 9: the various sets of good files (maybe 20GB altogether, for a single bad CD), produced by various reads and readers before and after buffing, are merged into a single good set with Beyond Compare.
Step 10: with Beyond Compare the mounted iso image (pre-buffing or post-buffing), containing the original structure of the CD/DVD, is compared against the set of merged good files (Step 9); and a list of missing files (= the bad files which could not be recovered from the bad CD/DVD) with filenames, bytes and dates is prepared manually.
Step 11: The files on the list of missing files are individually read from the bad buffed CD/DVD by Unstoppable Copier, with retries=99, and with all good readers. Any good, additionally recovered files are merged into the merged set of good files.
Step 12: Other possible sources (related CDs, older or newer versions of the software CD, google/bing, eMule, ftp search) are searched for the bad/missing files, with the same file name, file size in bytes and similar modification dates. This step can be crucial for repairing.of the CD.
In one recovery attempt 2 apparently good replacement files were found via google. Subsequently, however, continued buffing with the Aleratec machine produced 2 good files, which differed by 5 bytes in the header from the files found via google. The files recovered after buffing with the Aleratec machine and those found via google were .DL_ cab files and contained identical DLLs, so the slightly different replacement files found via google may perhaps have worked, even if they were not identical to the original files on the bad CD.
Replacement files from related CDs (e.g. CDs by the same software/CD producer, with different versions of the software, DLLs etc. tend to be re-used) have been the best source of good replacement files.
Step 13: Any found replacement files are compared in Beyond Compare/Hex Viewer against the corresponding file in the pre-buffing and post-buffing iso images. All bytes of the replacement files should be identical to the files in the mounted .iso, except for the zeroed out "holes" in the .iso files, i.e. the good sectors of the bad files on the .iso should be identical to those of the replacement files.
Step 14: a copy of the the pre-buffing (or post-buffing) iso image is opened in UltraISO. All files and folders of this iso image are deleted in the UltraISO window, so that an empty shell remains, with some of the properties of the original .iso file.The set of good merged files (files and folders) is then dragged and dropped into this empty shell. . Finally, this shell with the new content is saved as a new .iso under a different name, e.g. "repaired.iso".
Step 15: Integrity check with 7-Zip: all archive files (.DL_, .EX_,, .IN_ etc) in the mounted repaired .iso should extract without error messages, see http://www.msfn.org/...post__p__997941 There is a good chance that the repaired CD/.iso works as well as the original CD.
Step 16: file cleanup: delete again the various sets of of good files. There may be many files and folders to be deleted; during the recovery attempt of one CD (not DVD!), 21 sets of good files were deleted, with 100.000+ files. The recovery of a single DVD may require 100GB of free HDD space for maybe 20 sets of good files
The repaired .iso should contain the structure/shell of the original CD, the set of merged good files from maybe 20+ reads, and replacement files from other sources for the non-recoverable files.
This post has been edited by Multibooter: 18 May 2012 - 10:55 AM
Posted 16 May 2012 - 04:37 AM
"Verbatim DVD+R offer 4.7GB or 120 Minutes of write-once storage capacity, superior recording quality, and compatibility with 1X to 16X DVD+R writers. Verbatim's 16X cutting edge technology allows users to record a complete 4.7GB/120Min disc in approximately 5 minutes. Recognized as the choice for professional users, Verbatim DVD+R offers the optimal "Advanced Azo" recording dye, which provides the highest level of read/write performance, reliability, and archival life."
I ordered these (Verbatim 97459 4.7 GB) in Apr/May .... the DVDs with that number were made in Thailand.
I guess that Taiyo Yuden DVDs are maybe the best but these seem to be close for long lasting storage DVDs.
This was posted at Amazon about Verbatum DVDs made in India over Thailand or Asia ....
"I've used to have good success over the years with Verbatim quality and they used to be worth the extra few dollars. Sadly this is no longer the case, you may need to look elsewhere, I am disappointed.
This purchase from November 2010 shows the discs are now made in India, so even though they have the same product code as the ones that used to be made in Singapore or Taiwan, they are not up to the same standard."
... as I said earlier, the Verbatim 97459 DVDs that I got were made in Thailand. I had no idea when I placed the order where they were made until I received the shipment, first thing I looked for when I opened the box ... the "Azo" label and place of manufacture. Placed a second order after the price dropped again for part of a day a week or two later (below $22). Today, now they are $27.84 for 100 blanks.
Anybody with DVD info or experience with a good brand, I'd like to hear what you recommend or use. I have 400 of these Verbatum DVDs since the price on blank DVDs has jumped since last year.
This post has been edited by duffy98: 16 May 2012 - 08:44 AM
Posted 16 May 2012 - 11:33 AM
Why archive software CDs/DVDs?
First of all, as I mentioned above, I don't consider plastic media to be a good long-term storage solution. The purpose of my archiving CDs/DVDs onto HDDs is to get away from CDs/DVDs and other plastic media. In other words, I am migrating from plastic to HDDs. 1 HDD is easier to back up than 300 CDs/DVDs.
Here some advantages of CD-Rs and DVD-Rs, which are useful, but may eventually become legacy media, just like 1.44MB floppies or 240MB LS-240 diskettes:
a) CDs/DVDs are read-only media and stuff on them cannot be infected after burning; .exe files on an archive HDD can become infected by .exe infectors after archiving. I know of no malware which can infect .iso files, so stuff archived on a HDD as .iso is currently pretty safe. What I don't like about .isos is that there is no software which can repair damaged isos, at least as far as I know.
b ) CDs/DVDs are mechanically quite stable and don't die if you drop them
c) CDs/DVDs are a small separate storage media for stuff I don't want to have on my archive HDDs, like infected stuff, viruses, trojans, riskware, malware and other stuff. I keep, for example, on an especially marked CD some specimen of the Tenga virus, of Tenga-infected files and of possible causes of the Tenga infection, as souvenirs of a really bad infection 2 years ago. I also keep software containing password-protected stuff on a separate CD, one never knows what's in it.
d) you can dispose of CDs/DVDs quite easily in the garbage, or use them as coasters under your cup. Disposing of HDDs is a little more time-consuming, since they should be wiped before being taken to a recycler of electronic trash.
Other stuff I back up to CDs are photos and compilations of installation sources of actually used, good software, for convenience and as additional backups on different media. All my "Source" and "Photo" CDs are also archived as .iso on HDDs. I don't archive/back up stuff to DVDs anymore.
In the US I use Taiyo Yuden TYG02 DVD-Rs, which I bought from ebay as a cake of 100 about 3 years ago. In Europe I am using RitekG04 DVD-Rs, bought in a supermarket under the "Octron" label about 7 years ago. The Octron DVD-Rs had an excellent burn quality initially, but the burn quality of DVDs burnt from them has deteriorated steadily over the years, plastic media deteriorates regardless whether burnt or still blank. The whole issue of "burn quality" of plastic media is a time-wasting headache. With HDDs you don't have the issue of "write quality", at least it hasn't surfaced. I actually would prefer a 1TB HDD where the data stays Ok for 50 years, rather than a 50TB HDD, where the data stays Ok for 1 year. I have no idea whether there are HDDs with archival storage quality.
This post has been edited by Multibooter: 16 May 2012 - 01:13 PM
Posted 16 May 2012 - 02:06 PM
This post has been edited by duffy98: 16 May 2012 - 02:07 PM
Posted 17 May 2012 - 02:32 PM
This machine does work http://www.aleratec....isc-repair.html and http://www.amazon.co.../dp/B000E4K2GO/ . I have now repaired/recovered a 2nd CD, an old original, pressed MS Win95 OEM CD (file modification dates 11-Jul-1995, the CD had only ISO 9660, no additional Joliet, and was not bootable). The CD had developed by itself over time 2 cracks at the outer rim, and had also a couple of scratches. The DVD burner, which was the top reader of the first CD I had repaired (see above), was able to read only 62 out of 1535 files. The best reader for this particular bad CD was the blu-ray burner Pioneer BDR-203; the other blu-ray burner in my arsenal of excellent readers, an Asus BW-12B1ST, was just stuck reading the CD for maybe 1-2 hours, until I canceled.
I was able to create a good iso from this CD with this burner a year ago, but only during a single read of many. I wasn't able to read the CD properly again, so I had put it away, marked "unresolved problem, resolve it later". This iso was unfortunately created by UltraISO, so I didn't know whether the .iso was good or contained zeroes for bad sectors.
Buffing means here to remove a thin layer of the plastic of the CD with some kind of fine sand paper. I buffed the CD two times with the Aleratec, but the Pioneer blu-ray burner, which was my best reader of this particular bad CD, still created an iso with bad sectors with ImgBurn. Finally, after having buffed 5x, the Pioneer could read the CD properly, without bad sectors. The other burners could still not read the CD buffed 5 times. The previous CD (also pressed) which I had buffed and repaired before, also had started to become more readable after buffing 5 times. Each buffing cycle treats the bad CD for about 2 minutes with this special sand paper.
In the case of this 2nd bad CD, I did not need to use of the various sets of good files created by Unstoppable Copier, but the creation of these sets of good files with various burners had shown me which one of my burners was best at reading this specific bad CD. I knew in this way which burner to use to check whether the Alaratec had gone deep enough into the plastic of the CD, or whether I should keep on buffing.
The consumables (the wheels with the special sand paper and the polishing paste) are quite expensive, so the cost of materials for creating a good iso from this CD was maybe $3, plus 3 hours of fiddling around.
The Aleratec is highly recommended, probably the best of its kind. The only critique: the power supply is only 110V and it's inconvenient to switch between the 2 sets of wheels in the repair process. I will eventually buy a second unit.
Blu-ray disks are not on the list of media which the Aleratec can repair, so blu-ray disks are probably unrepairable media. Before repairing bad CDs/DVDs or recovering data from them, one should ask oneself: Is the stuff on the CDs/DVDs really worth the time and effort?
This post has been edited by Multibooter: 17 May 2012 - 05:19 PM
Posted 18 May 2012 - 12:47 PM
Posted 18 May 2012 - 06:07 PM
I had tried CDCheck v3.1.14 http://www.kvipu.com/CDCheck/ two years ago, but rejected it. The files "recovered" by CDCheck may NOT be correct, and sometimes differ from the files recovered by Unstoppable Copier (with the setting "Auto Skip Damaged Files") or recovered by Beyond Compare. When a file is recovered as a "good" file by Unstoppable Copier or Beyond Beyond Compare, it is good, you can count on it. On the other hand, I could not extract some cab files "recovered" by CDCheck, while their counterparts recovered with Unstoppable Copier or Beyond Compare could be extracted.
I had also tried Dead Disk Doctor v1.26 http://www.deaddiskdoctor.com/ two years ago, but the files it recovered, over and above those recovered by Unstoppable Copier or Beyond Compare, were bad. A test-installation, for example, of a software containing such a file "recovered" only by Dead Disk Doctor resulted in the termination of the software installation. Dead Disk Doctor resolves the issue of what to do with the areas corresponding to bad sectors in an interesting way: bad areas are apparently filled with random characters, which may be useful for movie DVDs, but not for software CDs/DVDs.
The key to the recovery/repair of a bad CD/DVD is not software, but hardware. Since 2 programs work fine and reliably (Unstoppable Copier and Beyond Compare), I see no point in looking further for something which doesn't enhance the recovery/repair of a bad CD anyway.
This post has been edited by Multibooter: 18 May 2012 - 06:11 PM
Posted 18 May 2012 - 09:36 PM
"In addition, with the rapid acceptance of recordable DVD, no one has done an extensive evaluation of the dozens of brands of DVD-R/-RW/+R/+RW/RAM discs now available for preserving video at home on DVD." I have been following, for at least 8 years, the very detailed tests and evaluations of CDs, DVDs etc. of the German Computer Bild, which is Europe's best-selling computer magazine, bi-weekly about 100 pages each, paid circulation 540.000, published in nine countries, not dead yet http://de.wikipedia....i/Computer_Bild , unlike the computer magazines in the US, rest in peace.
Here the current rankings and evaluations of DVD media in their tests: http://www.computerb...Ds-3913586.html
The top ranking DVD+R has a rating of only 2.85 (scale: 1=excellent, 6=trash). I wouldn't buy a product with such a poor rating by Computer Bild, unless there were special reasons. If you look at the color of the ratings (this needs no translation from German), the top ranking DVD was rated as belonging to the yellow zone (green - yellow - red). There was no DVD brand in the green zone.
This post has been edited by Multibooter: 18 May 2012 - 09:49 PM
Posted 19 May 2012 - 12:04 AM
I just gave up on recovering a bad Memorex DVD+RW (re-writable), burnt in February 2004, 8 years ago. It contained 4.1GB of data, altogether 17 zipped up system backups. The DVD+RW was accessible in only 1 of my 5 excellent readers, an Asus blu-ray burner BW-12B1ST, which seems to be good at reading +media. 2 good readers capable of DVD+RW wouldn't even recognize that a DVD was inserted. The silver color of the front side of the DVD, where "Memorex - is it live or is it a Memorex?" was printed, had turned a little yellowish, aging plastic.
The Asus blue-ray burner with Unstoppable Copier was able to recover 3 good zip files, altogether 735MB, so about 80% of the data on the bad DVD+RW was lost. I had a note on a piece of paper with this bad DVD, dated December 2006, indicating that the content of the DVD was still Ok (binary compare) 2 1/2 years after burning. It is interesting to note that adding a 3% recovery record with WinRAR to a .rar file is of little use if the file is stored on a CD/DVD and the whole file becomes unreadable.
I had buffed the bad DVD+RW with the Aleratec, altogether 5 times, and each time the recovery got worse. I decided to give up on the recovery, the remainder of the data was probably unrecoverable, and I had a still good backup on a second DVD-R.
When I burnt backup DVDs, about 5 to 8 years ago, I ALWAYS burnt 2 identical good copies, in case one goes bad. Usually I burnt more than 2 copies, on top-rated media with a burner which "liked" the particular media, until the burn quality with Nero Speed Disk was 95-98/100, and then discarded those DVDs with a lower burn quality. I have transferred the content of maybe 80 old DVDs, burnt between 2003 and 2007, onto external HDDs over the past 2 years. It was probably the last call, even if the DVDs were stored in slim cases in a cool place. The disk quality, as measured by Nero Speed Disk, had gone down to zero with most DVDs. Maybe 10 of these 2x80 DVDs had serious read issues and 5-10% of the archive would have been lost if I had not burnt 2 backup DVDs for each set of data backed up.
I hope that the transfer from plastic media to HDDs will be complete by the end of this year, it's a quite time-consuming undertaking.
This post has been edited by Multibooter: 19 May 2012 - 09:58 AM
Posted 21 May 2012 - 02:35 AM
As I mentioned above, I always created 2 backup CDs/DVDs of each set of data to be backed up. But I have one pair of DVDs where 1 file differs. The file in question is a 691MB .ace archive file and contains inside a .ccd image (CloneCD) of a CD. On one DVD the 691MB .ace archive extracts fine, on the other DVD the .ace archive is broken and doesn't extract. A binary compare with Beyond Compare/Hex Viewer indicates that the two .ace files have different non-zero content in one contiguous block of 362 bytes.
Here the history of the "bad" DVD containing the broken .ace archive:
This DVD was burnt on 26-Aug-2006 as replacement of another backup DVD, burnt about a year earlier, because the disk quality of the initial DVD had deteriorated substantially. This replacement DVD, containing the corrupt .ace archive, was burnt with Nero v220.127.116.11, by first creating with Nero "Image Recorder" a temporary .iso of the deteriorating original backup DVD and then burning the replacement DVD from this .iso. I then made a binary compare of the burnt replacement DVD and the .iso, mounted with Alcohol, which was Ok, and I noted this on the DVD. This replacement DVD had a disk quality of 95/100 just after burning, measured with Nero CD-DVD Speed v18.104.22.168. I have just re-checked its disk quality with the same tool, it is currently, 6 years later, 48/100, still in Ok condition. So why did the "bad" DVD contain a broken archive?
I checked my notes for 26-Aug-2006 and actually found 2 cryptical entries "Nero burns not-identical files, no msg" and another entry that I had rejected on that day a Targus 7-port USB hub Model PAUH212, "does NOT work with Belkins USB 2.0 PC-Card, problem with Nero when using Adaptec USB 2.0 PC-Card: large files on burnt DVD are incorrect, without a message (found out with binary compare)". I apparently had suspected a hardware problem to be the cause of the non-identical files. I remember vaguely to have repeated the burning of the DVD from the .iso, and that the binary compare against the .iso was Ok, but the binary compare against the other backup DVD showed a difference. I had no explanation for this difference, and couldn't decide which one of the 2 DVDs was better, so I kept both versions. After I stopped using the Targus hub, this burn problem didn't occur anymore. The real reason, however, that this problem didn't come up anymore was probably that I haven't burnt replacement DVDs after that experience, checking disk quality and re-burning CDs/DVDs was just too time-cvonsuming.
Looking back, I probably made the wrong conclusions 6 years ago. Today I would rather speculate that Nero v22.214.171.124 "Image Recorder" had an issue reading the deteriorating original DVD and created somehow an iso with 362 contiguous wrong bytes. A binary compare of the DVD burnt from such an iso against the same mounted .iso would then be identical, and a binary compare against the other good backup DVD would show differences. But I have no idea why this area with bad data was only 362 bytes, not a whole 2kB sector,
I suspect that the gradual decay of plastic media is a major cause of broken archives. At eMule maybe 5% of archive files (zip, rar) are broken. Maybe the great number of different versions of an mp3 at eMule, often between 10 and 30 different version for one original mp3, is brought about by the decay of plastic and the selection of the option "Ignore read errors" when CDs are copied. MP3Test, for example, is a very good tool to test mp3 files for corruption.
I was able to repair with WinAce v2.6 the broken 691MB .ace archive on the "bad" replacement DVD. The .ccd image extracted from the repaired .ace was identical to the .ccd image contained on the other good backup DVD.
This post has been edited by Multibooter: 21 May 2012 - 02:43 AM