Fatal Disk Error urgency [1]

[aboulang@BBN.COM]

   Date: Tue, 12 Jun 90 01:17 EDT
   From: "Robert W. Kerns" <RWK@fuji.ila.dialnet.symbolics.com>

 
   1) If the LMFS does not come up at all, you're in serious
   trouble.  LMFS:FIX-FILE won't help you.  Use SI:FIX-FEP-BLOCK.

   If its read/write test finds that the data was bad but the block
   is good, try bringing up the LMFS again.  If you're very lucky,
   you may be able to bring it up and do a backup.

   If the block is physically bad, choose the COPY option, and try
   bringing up the LMFS again.  Immediately do a backup, if you
   succeed in bringing it up.



As a survivor of a crash where the LMFS would not come up, one can do
some things if you can *NOT* get the LMFS up. Find out where it is
stopping in the bring-up process. In my case, it was stopping in
bringing up one of the partitions.  My ultimate problem turned out to
be a bent pin on one of the disk drive cables. ECC was amazing - it
tried real *HARD* to adapt to this noisy problem. It managed to mess
up the partition table info and the free block list of one of the
partitions. I rebuilt the partition info (there is low level support
for doing this) and conservatively rebuilt the bad part of the free
block list. I spent a couple of days with intermittent low-level write
problems in trying to rebuild everthing until it occured to me to
check for intermittent physical problems. After I found the pin a was
able to write out the free block list and the LMFS came up! I then
reclaimed mismarked blocks by using the salvager.


Happy bit-twiddling and pin bending,

Albert Boulanger
aboulanger@bbn.com