LMFS repair

[David Gadbois]

I have a large LMFS with partitions spread over several disks. One of
the disks has bought the farm. The last time I had to do a full
restore [1], it took a couple of days, and the LMFS was much smaller
then. It occurs to me that it may be possible to simply dike the
partition on the bad disk out of the FSPT and somehow recover from
there. Is it possible? Any advice?

Thanks,
--David Gadbois

[1] Seven years ago. My, those lispms are sturdy.

[re...@wilson.ai.mit.edu]

Date: Wed, 8 Apr 1998 10:45 EDT
From: David Gadbois <gad...@cyc.com>

I have a large LMFS with partitions spread over several disks. One of
the disks has bought the farm. The last time I had to do a full
restore [1], it took a couple of days, and the LMFS was much smaller
then. It occurs to me that it may be possible to simply dike the
partition on the bad disk out of the FSPT and somehow recover from
there. Is it possible?

Yes, but tricky. (I've successfully done it, but that was a long time
ago and my recollection might well be faulty.)

The essential element is to replace the failed partition in the fspt
with another equal or larger-sized zeroed partition on a new disk. The
various partitions are relatively ordered, and the LMFS startup code
needs to thread them together in the proper order, so the broken
partition needs a placeholder.

Once you've done that, there might be a couple of startup transients
you'll have to proceed past to get the LMFS up. Once past that, you'll
have a LMFS where all the file pointers to that partition will get
checkwords errors, including pointers to directories. How much of
your original LMFS hierarchy will be intact will depend on how much of
your directory structure (i.e. the directory files themselves) was on
your broken partition.

Run check records. This will identify all the "files" whose contents
are no longer there, because the partition vanished. Use LMFS::FIX-FILE
to get rid of them.

Then run the salvager. It will find all the orphaned files, and put them
back into the directory hierarchy.

Any advice?

Good luck. Feel free to call or write if you need more help.

Kalman Reti
Symbolics
re...@symbolics.com
781-937-7655