[Info-vax] Best way to get what I can off a failed VMS Disk?

[Michael Moroney]

"geze... at rlgsc.com" <gezelter at rlgsc.com> writes:

>On Saturday, October 24, 2020 at 8:49:42 AM UTC-4, Chris Townley wrote:
>> I have a failing ODS-2 disk in my Alpha (HPE VMS 8.3)

>> What is the best way to recover those files that are recoverable, with
>> the drive going into mount verify?

>> Thanks

>> Chris
>Chris,

>It depends upon the reason for the MOUNT verify. If the problem is one or a few bad 
>blocks, it may be possible to reconstruct by obtaining information from an earlier backup 
>and doing a form of custom merge. It can be done, but it is a tedious process.

>For a start, I would try to see if it was possible to MOUNT/FOREIGN/NOWRITE and do a 
>physical BACKUP of the drive.

My personal suggestion, if you have the hardware, would be to do the MOUNT/FOREIGN/NOWRITE 
and BACKUP/PHYSICAL to a new drive, then do a BACKUP/PHYSICAL to a seccond new drive.

Try to recover from the second backup drive and do all manipulation (such as 
ANALYZE/DISK/REPAIR or poking at things like INDEXF.SYS if you know how) only to the
second drive. That way if you somehow make things worse, MOUNT/FOREIGN/NOWRITE the
first backup drive and create the second backup drive again, in other words start over.
That should be the only time the first backup is used, and you'll still have whatever was
pulled off the bad drive the first time.  Depending on the exact failure, the original
bad drive may become unusuable after more usage.

I did this when on my hobby system something scribbled all over part of INDEXF.SYS on one 
drive and this lost access to many files as well as others became "lost" files when their 
directory header got scrozzled. I know the bits would be there until an ANALYZE/DISK/REPAIR 
would free any "incorrectly allocated" blocks.

DFU on freeware may also be useful.