(I had accidentally sent my reply below only to Antonio. I'm resending
it to the list.)
On 10/05/2021 10:05, Malte Dehling wrote:
Thanks a lot, Antonio, these are very valuable to
have!
I've only checked a couple of them under SIMH, so it would be helpful to
know if I need to check my workflow or not.
I think uploading them to
archive.org would be a
good long-term
solution. I can take care of it if you don't have an account.
Please do. Thanks.
Will do. I'll let you know.
In other news, I polished the MAR-1989 CONOLD, which
looked very bad, to
start with. Amazingly it buffed up quite nicely and then read surprisingly
well:
[
$ ddrescue -r5 -v /dev/sr1 CDROM-AG-NC67A-RE-1989-03-VMS-CONOLD.iso
CDROM-AG-NC67A-RE-1989-03-VMS-CONOLD.map
GNU ddrescue 1.23
About to copy 205199 kBytes from '/dev/sr1' to
'CDROM-AG-NC67A-RE-1989-03-VMS-CONOLD.iso'
??? Starting positions: infile = 0 B,? outfile = 0 B
??? Copy block size: 128 sectors?????? Initial skip size: 128 sectors
Sector size: 512 Bytes
Press Ctrl-C to interrupt
???? ipos:? 205198 kB, non-trimmed:??????? 0 B,? current rate:?????? 0 B/s
???? opos:? 205198 kB, non-scraped:??????? 0 B,? average rate: 637 kB/s
non-tried:??????? 0 B,? bad-sector:???? 2048 B,??? error rate: 170 B/s
? rescued:? 205197 kB,?? bad areas:??????? 1,??????? run time:????? 5m 22s
pct rescued:?? 99.99%, read errors:?????? 25,? remaining time:???????? n/a
????????????????????????????? time since last successful read:????? 2m? 1s
Finished
]
So I went ahead and tried the CONDIST from MAY-1989. That too now can be
read, although it is proving a somewhat tougher nut to crack:
[
$ ddrescue -r5 -v /dev/sr1 CDROM-AG-MN36D-RE-1989-05-VMS-CONDIST.iso
CDROM-AG-MN36D-RE-1989-05-VMS-CONDIST.map
GNU ddrescue 1.23
About to copy 623247 kBytes from '/dev/sr1' to
'CDROM-AG-MN36D-RE-1989-05-VMS-CONDIST.iso'
??? Starting positions: infile = 0 B,? outfile = 0 B
??? Copy block size: 128 sectors?????? Initial skip size: 128 sectors
Sector size: 512 Bytes
Press Ctrl-C to interrupt
???? ipos:??? 5919 kB, non-trimmed:??????? 0 B,? current rate:?????? 0 B/s
???? opos:??? 5919 kB, non-scraped:?? 11127 kB,? average rate: 14694 B/s
non-tried:??????? 0 B,? bad-sector:??? 2843 kB,??? error rate:????? 85 B/s
? rescued:? 609276 kB,?? bad areas:????? 445,??????? run time: 11h 31m? 2s
pct rescued:?? 97.75%, read errors:???? 5884,? remaining time:? 5d 23h 43m
????????????????????????????? time since last successful read:????? 2m 45s
Scraping failed blocks... (forwards)??? ]
On the plus side, that's 97.75% more data than I had before :-) but the
"remaining time" looks like it could be the rest of the week (it varies
quite a bit).
I think, from reading the manual, that I can use CTRL-C and restart this
again later and it will pick up where it left off using the map file. Is
this right?
Very nice, this worked much better than I had expected! And you're
right, you can simply CTRL-C and restart ddrescue with the same command
(i.e., with the iso and map file; different options should work.) I would
make a copy of the files before restarting, just in case.
Are there any other options I should consider trying?
Can you try with "-b 2048 -d" for direct disc access and maybe once more
with "-R" for reverse?
Another thought is that perhaps a shade more polishing
might help. If I
polish the CDROM a little more and then resume the ddrescue, I think I won't
be any worse off than I am now, i.e. all existing data will still be there
and all I'll be risking is data that maybe would have eventually read before
but now may not read at all. Is that right? Successful reads are now ~20m
apart, so I suspect that the remaining data will be quite difficult to
recover.
After trying the various options on the disk in its current state, I see
no harm in trying this approach. With the map file, ddrescue should
never overwrite already-read data. Again, I would make a copy to be
safe.
Cheers,
Malte
--
Malte Dehling
<mdehling at gmail.com>