Path: utzoo!utgpu!water!watmath!clyde!cbosgd!ucbvax!CITHEX.CALTECH.EDU!carl
From: carl@CITHEX.CALTECH.EDU (Carl J Lydick)
Newsgroups: comp.os.vms
Subject: Re: Repairing disks with corrupted index files
Message-ID: <880109071621.025@CitHex.Caltech.Edu>
Date: 9 Jan 88 15:32:03 GMT
References: <2471@trlsasb.oz>
Sender: daemon@ucbvax.BERKELEY.EDU
Distribution: world
Organization: The ARPA Internet
Lines: 38


 >  We have an eagle disk with a SI 9900 controller which has had it's index file
 > corrupted 4 times in the last 4 months. Has anybody else experienced these
 > problems. Is it a software or hardware problem.?

We've had similar problems.  In both cases, it appears to have been a hardware
problem.   On  one  system, we had a crash resulting from a machine check, and
when the system came up again, the  disk  was  corrupted.   This  is  not  the
problem you're having, presumably.

 >  The error message I get when I try and mount the disk is
 > BITMAPERR- I/O error on storage bitmap; volume locked

On the other system, one of the servo boards for the Eagle in question failed.
The result was that we could read the home block on the volume (you can
check this by doing a MOUNT/FOREIGN: if it works, you can read the home
block), but we couldn't read the BITMAP or the bad block track (you obviously
can't read the BITMAP; to see if you can read the bad block track, mount
the disk/foreign, and try doing a physical backup).

 >  Now the system error message manual implies you can repair this by
 > using the verify utility but the catch 22 is that you have to mount
 > the volume files-11 ... and the mount won't let you do this.
 >  Is there a way of repairing a disk with a bad index file ?

This depends on just how bad the I/O error is.  If you just have trouble  with
the  bitmap,  mount will succeed, but with the volume locked against extending
any files.  You can then  run  verify  and  fix  the  problem  (unless  you've
actually got a bad block in the bitmap; in that case, do an image backup, then
run EXOR on the disk to reformat it [you should do this  if  the  disk  hasn't
been  formatted  in  the  last  few  years;  if you can't remember when it was
formatted, it's due for reformatting] and find the bad  blocks  on  the  disk,
then restore the saveset).

On the other hand, if you can't read anything except the track with  the  home
block  (and it sounds like this is your problem), you should have the hardware
problem repaired (as I said above, this is probably a problem with the servo),
and then run verify on the disk.