Hi all
Many thanks to those who replied - got one response almost imediately!
From: "Murphy, Ed" <Ed.Murphy_at_ussc.ussurg.com>
>From alan_at_nabeth.cxo.dec.com Tue Jun 24 09:41:52 1997
From: James Sainsbury <sainsb_j_at_chem.usyd.edu.au>
first a copy of the question:
> Before giving up on the data, I was wondering if there is any way to
> recover data off an optical disk when the summary file has been
> corrupted. (A search of the archives didn't reveal much).
>
> The messages we get are an I/O error when we try to mount it
> and an fsck told us it was unmounted cleanly but the summary file
> was bad - as well as a number of blocks - altho not the superblock.
>
> Any hints of how - if possible - to recover the data would be
> greatly appreciated.
And now the summary and solutions:
************************ Me *************************************
Unfortunately necessity is the mother of motivation as well as invention.
Altho I did try Jame's method last night - to no avail because the computer
would never mount the optical disk in read or write mode - an old backup
of the disk was found this morning. It seems the data was on a disk
back in march, moved to an optical platter for space and then removed
from disk. Fortunately someone (not me :)) was behind on backups...
James has outlined a good method of recovery.
Ed has provided the phone number of a disk recovery company.
and alan suggested a device error - the uerf file indicated a hard error
detected, meduim error -unrecoverable. Other optical disks are still
mountable and readable so it really just is the one disk has an error
that has killed the disk side - reformatting will begin after i get back
from my week and a half vacation.
for those curios, an optical platter is kinda like a glass disk.
they are mounted in a drive that makes them act like a (slow) disk drive -
they are mounted and unmounted in d.u. the same way. they are best for
stuff you need to get at in the way you access a regular drive, but don't
want to have on disk for space purposes. Or at least that is how we use
them here. Oh, don't drop one or you will have to say bye bye data
and no way to recover it!
Thanks again
Claudia
************ James Sainsbury <sainsb_j_at_chem.usyd.edu.au> *************
Just had the same thing on an SGI.
A skeleton of one approach:
0) to set the disk cartridge to readonly
1) Find a hard disk partition big enough to hold the filesystem on the MO disk
2) Use dd to copy the filesystem from the MO drive to the hard disk partition
thus creating a byte for byte copy of the MO filesystem.
3) Running fsck on the hard disk partition copy
4) If that fails try fsdb to have a poke about the filesystem - this requires
looking at the #include files from /usr/include/ufs/*.h to make sense
of the data structures.
*************************** alan_at_nabeth.cxo.dec.com *************************
What file system is on the disk? UFS, which uses fsck,
doesn't have a "summary file". If it isn't UFS on the
disk you should be running fsck on it. The fact that
you're getting I/O errors suggests a device problem,
which would cause any file system fits. Look at the
error log to see what the error is. If using uerf(8)
use the option "-o full" to get the full listing.
**************** "Murphy, Ed" <Ed.Murphy_at_ussc.ussurg.com *************
Hello Claudia,
We've used a company by the name of Advanced Data Recovery to pull
data off corrupted disks. Their number is (800)301-3282.
Good luck,
Ed Murphy
Manager Systems Integration
United States Surgical Corporation
(203)834-5216
Received on Tue Jun 24 1997 - 20:01:32 NZST