Re: formating a disk

[TYSON@ai.sri.com (Mabry Tyson)]

    Date: Wed, 26 Jun 91 12:40:52 EST
    From: bouma@cs.purdue.edu

    I had this disk drive that was really messed up after a power outage
    so I did a "disk format" on it.  Now I understand that to get the
    initial FEP filesystem on it I have to do a "disk restore" from the
    IFS tape.  The "disk" commands are in a file "g208-disk.flod".

I recently had another site ask about a disk problem.  They wanted to format
the disk too.

These aren't floppies!  You can't just format the disk and expect to run
and rebuild everything.  It is a difficult process to rebuild a disk and
usually requires a working machine that can have the bad disk as a second
disk drive.  *IF* you have the IFS tape and a breath-of-life tape, then
maybe you can do it on a single host with a single disk.

There are a number of problems that can appear to be drastic disk failures
that really aren't.  The most common would be getting a ECC error during
running (esp on 3600/70/40 class machines).  Even if your disk reports
problems while trying to read your world, you're much better off not
formatting the disk until you know exactly what your options are.

(For example, in that case, if I had no other world to boot or netboot
and I can't get into even the barest of lisp worlds by cold booting or
warm booting, I'd first try reformatting that portion of the disk with
problems and then reloading.  Another option would be to load a world into
what was your swap space and use your old world as swap space.  You can do
lots of things once you're into Lisp.  I've rebuilt the IFS on a running
machine's only disk so it recognized some new bad blocks.)

Summary:  Don't format unless you know how to get you running again.
Even if you don't have a service contract, it is probably a good idea to
get Symbolics Customer Service to help you.

P.S.  I always keep a second set of FLODs, a second microcode, and a
second world (netboot worlds are real small) on our machines.  I should be
able to recover from any single disk block or track failure without much
problem.  I also store my IFS tapes in a safe place.