BetaArchive Logo
Navigation Home Screenshots Image Uploader Server Info FTP Servers Wiki Forum RSS Feed Rules Please Donate
UP: 31d, 17h, 44m | CPU: 43% | MEM: 2667MB of 4597MB used
{The community for beta collectors}

Post new topic Reply to topic  [ 3 posts ] 
Author Message
 PostPost subject: Help with fixing bad sectors on dumped cd image        Posted: Fri Feb 02, 2018 8:48 pm 
Reply with quote
Donator
Offline

Joined
Tue Jun 16, 2009 11:40 pm

Posts
70

Favourite OS
whistler
Hello,
recently I bought windows 95 OSR2 cd, which was scratched. I tried to make mdf on multiple drives, but best result I got was 6 undreadable sectors all belonging to one file (welcome video). I noticed that from 5 dumps I did, only one sector was unreadable on all of them. So then I opened image files in HxD editor and copied over sectors that were read properly in other dumps. For the last one, I went to my OSR 2.1 disc, which contains file of identical size (just different timestamp), went to proper sector and copied that over. After I saved and mounted that fixed image, I am still unable to copy problematic file. Am I missing something?

thanks.


Top  Profile
 PostPost subject: Re: Help with fixing bad sectors on dumped cd image        Posted: Sat Feb 03, 2018 2:34 pm 
Reply with quote
FTP Access
User avatar
Offline

Joined
Sun Mar 16, 2014 6:56 am

Posts
148

Favourite OS
DOS
What does "unable to copy" mean - you can't copy it in Windows Explorer, or Windows Setup can't copy it from the CD while installing?

Either way, I probably don't know how to help you fix that image, but maybe something will come to mind later.

What I'd do is try using the Linux tools dd_rescue or ddrescue. I prefer the latter because it will save a log of which sectors it was unable to read (or didn't read because you stopped it part way through) so that you can run the tool again later and it will just try to read the missing sectors. These tools do things like retries for reads, trying to read the sectors starting from the end of the disc instead of the start, etc. I've never actually used them for CDs or DVDs, only hard disks, but I can't see why they wouldn't work for CDs/DVDs too. Also, they'll only give you an .iso image.

A bad CD/DVD is probably a good first project for learning those tools because you can play around with the options, and not worry about how many times you start over, not like with a failing hard disk where you want to get the data off ASAP in case it only has a few minutes or sector reads left before it dies completely!


Top  Profile
 PostPost subject: Re: Help with fixing bad sectors on dumped cd image        Posted: Sat Feb 03, 2018 2:55 pm 
Reply with quote
Donator
Offline

Joined
Tue Jun 16, 2009 11:40 pm

Posts
70

Favourite OS
whistler
It means windows explorer wont copy the file.

I did some more investigation and to put it simply, converting my modified mdf to iso fixes the sector issues and restored file has correct hash. But it results in loss of subchannel data. With the sectors I took from another dump attempts, it seems that just recreating mds file might be solution, for last sector I took from another disc it needs some more fiddling with ECC or something (converting mdf to bin/cue still rendered read error in that sector)

My question then, is it possible to somehow create correct subchannel data for sector inserted from another disc and then regenerating mds file? Like burning the fixed iso and then dumping it back, modifying that last sector in original mdf and taking mds file.


Top  Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 3 posts ] 




Who is online

Users browsing this forum: No registered users and 10 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to:  

All views expressed in these forums are those of the author and do not necessarily represent the views of the BetaArchive site owner.

Powered by phpBB® Forum Software © phpBB Group

Copyright © 2006-2018

 

Sitemap | XML | RSS