Subject: dump problem
To: None <current-users@NetBSD.ORG>
From: John F. Woods <>
List: current-users
Date: 08/24/1995 22:42:58
Are there any known problems involving dump (or restore) and
multi-volume dumps?  I used dump to back up a filesystem of about
480MB onto QIC 150 tapes (6250 types, 250M capacity each).  I used a
dump command of 
	dump -0u -B 245000 -f /dev/rst0 /dev/rsd3f
to create the dump; dump announced that it was going to write around
600MB worth of stuff and estimated 2.57 tapes.  (Quick observation:
the media for which dump has builtin defaults appear to have died out
in the Pleistocene Era.)  (I assume the astonishing inflation there is
because it was my netnews disk, average file size a hair over 2KB, so
plenty of per-file overhead).  When the dump was completed in about an
hour and a half I unmounted the filesystem, did a newfs (to change the
blocksize and increase the number of inodes), and then started
restore.  (Next quick observation:  always remember to set a large
tape record size on QIC tapes.  It took 6 hours or so for the restore
to complete, because the tape was constantly rocking!)

Partway through the first tape, I was greeted with a message about how
it was expecting inode N, but saw inode N-1.  (The filesystem was
live, but it should have been idle;  all producers and consumers of
news had been shut down.)  No other messages came out, so I forgot
about it.  Finally, it asked for tape two, I slammed it in, and went
to sleep (1AM).  When I woke up, I discovered messages on the screen
about how it couldn't find inode 85698, but it DID find 7, 8, 9, and
a bunch of other low numbers; this was followed by a series of
messages about files it couldn't extract because they weren't on the
tape.  Bracketing this was a pair of "restore: skipped one block"
messages.  I wrote down the messages, threw in the third tape, and let
it finish (no more noise).

Surveying the damage later, I discovered that the first 12 files on
the second tape hadn't been restored (thank goodness they were all
pure ASCII, I was able to reconstruct them from the raw tape easily).
The first file on the tape *sort of* got restored; its length was
correct, but it contained garbage, nonsense left over from files early
on the first tape.  The other 11 files at the beginning hadn't been
restored at all.  All the subsequent files were OK.  (Hmm, I still
haven't checked on the inode that it complained about early on...)

The first tape appears to end on a file boundary; there's a complete
file at the end (which was extracted), followed by NUL bytes to pad to
a 10K record boundary.

So, has anyone else had trouble with multiple tape dumps?  I haven't
erased these tapes yet, if there's any information you think I should
look for that would help.