ANK@CUNYVMS1.BITNET.UUCP (02/18/87)
There comes a time when all of us are forced to use old disks, or
disks that have something that one does'nt need.
So, we had an unfortunate crash, and a new DRA0: or
SYS$SYSTEM disk had to be made from a backup.
Our strategy has been to backup DRA0: every time we upgrade
a VERSION.Due to disk-shortage we used an old DISK having an old
version of UNIX System V. Well there seem to be no BADBLK.SYS .
Copying from old disks do not seem to work either.
It has been suggested that it comes with the disks.
Is it true that we cannot salvage a disk containing Unix even after
we delete all files and initialize it ? Or is there a documenatation
in the VAX/VMS reports that we missed ???
Thanks
Anil Khullar
------------------------------------------------------------------------
oberman@LLL-ICDC.ARPA.UUCP (02/18/87)
>There comes a time when all of us are forced to use old disks, or disks that >have something that one does'nt need. So, we had an unfortunate crash, and a >new DRA0: or SYS$SYSTEM disk had to be made from a backup. > >Our strategy has been to backup DRA0: every time we upgrade a VERSION.Due to >disk-shortage we used an old DISK having an old version of UNIX System V. Well >there seem to be no BADBLK.SYS . Copying from old disks do not seem to work >either. > >It has been suggested that it comes with the disks. Is it true that we cannot >salvage a disk containing Unix even after we delete all files and initialize >it? Or is there a documenatation in the VAX/VMS reports that we missed ??? You're close. It's not the lack of BADBLK.SYS that is bothering you. BADBLK.SYS is a VMS file and is never on a disk until after initialization. What is missing is the Manufacturer's Bad Block information which is (was?) written on the last track of the disk when the manufacturer checked the media prior to shipping. This information is also missing from many and perhaps all disks purchased form third parties. BAD performs a scan of the entire media to confirm that it may be written and read back. It starts with the assumption that the blocks called out in the manufacturers area are bad. If it can't find this information, it gets upset. At initialization time, VMS takes the contents of this area and and combines it with a similar area called the User Bad Block information to create BADBLK.SYS. This is a pseudo-file containing all of the blocks flagged in either of the bad block areas. UNIX is not aware of this bad block information and treats the last block like any other on the disk. This will surely clobber anything that was there. As a result, BAD can't be run on the disk. While the information that may have been in this area is lost forever, I believe that this area may be recreated by one of the diagnostics. Either EVRAA or EVRAC. I think the required section is PACKINIT. If you lack DEC diagnostics, many third party disk vendors supply code to perform this function with their systems. I know SI does. R. Kevin Oberman LLNL arpa: oberman@lll-icdc.arpa (415) 422-6955 I believe the above information is accurate, but I wouldn't bet my life on it. Your's on the other hand... ------