MATLEVAN@EKU (Jerry LeVan) (10/13/90)
Hello,
Here are some of my observations with trying to deal with
multitape backups with the Apple 40 meg tape drive.
My test bed is my X11R4 disk, an 80 meg apple hd80sc with
a maximal Aux partition with no mac partition.
cpio:
This program evidently cannot deal with multiple tapes
tar:
tar cvbBf 16 76200 /dev/rmt/tc1 .
This command started the backup and asked for a second
tape. Somewhere in the second tape I got a core dump
tar cvbBf 16 76200 - . | tcb > /dev/rmt/tc1
The above command seems to fill the first tape ok and
then asks for a second tape. The first write to the second
tape always causes an error and the backup aborts.
pax:
pax -w -b 8k -v -f /dev/rmt/tc1 .
This command correctly asks for a second tape. (I calculated
that the backup should take two tapes). The program does not
appear to terminate cleanly, by this I mean that when the
backup is complete the program will ask for another tape,
write nothing and immediately ask for another tape (indefinitely).
The program took about 2.5 hours to copy 67+ megabytes.
When I attempted to read the tapes for a table of contents
I found that I had to use the "dd" command and pipe the
results into the pax command, here is what I used:
dd if=/dev/rmt/tc1 ibs=40*8k | pax -v
This is what happened:
...
...
...
-rw-r--r-- 0 levan family 11528 Apr 23 16:13 ./src/mit/fonts/bd
f/m
isc/clR8 x13.snf
-rw-r--r-- 0 levan family 12040 Apr 23 16:14 ./src/mit/fonts/bd
f/m
isc/clR8x14.snf
pax: - : This doesn't look like a tar archive
pax: - : Skipping to next file...
120+1 blocks in
77248+0 blocks out
pax: Ready for volume 2
pax: Type "go" when ready to proceed (or "quit" to abort): go
pax: [offset 37m+736k+0] Continuing
pax: Ready for volume 3
pax: Type "go" when ready to proceed (or "quit" to abort): go
pax: [offset 37m+736k+0]: Continuing
pax: Ready for volume 4
pax: Type "go" when ready to proceed (or "quit" to abort): go
pax: [offset 37m+736k+0]: Continuing
pax: Ready for volume 5
pax: Type "go" when ready to proceed (or "quit" to abort):
Note that the second tape was not read ( I immediately
got the request of the third tape, typing go caused the
next tape to be asked for etc... There does not appear to
be a way to access the second tape.
I tried giving the command(with the second tape installed)
dd if=/dev/rmt/tc1 ibs=40*8k | pax -v
pax: - : This doesn't look like a tar archive
pax: - : Skipping to next file...
-rw-r--r-- 0 levan family 13064 Apr 23 16:14 ./src/mit/fonts/bd
f/m
isc/clR8x16.snf
...
...
This seems to pick up properly, examining the directory reveals that the
"last" file on tape one is in the directory immediately followed by
the "first" file extracted (OK listed) on the second tape. Maybe
it is possible to do a multitape restore.
Is pax and tar smart enough to not split a big file across
multiple tapes? Or is there some sychronization mechanism
which allows restoring file split across multiple tapes?
dump.bsd:
This program has trouble with specifying the size of the
tape by using the "c" option or any of the explicit size
settings using a byte count. Apparently one can lie also
by setting the density and length arguments, here is
what I used.
# dump.bsd -T5.2 0bsdf 8k 542 12500 /dev/rmt/tc1 /dev/dsk/c5d0s0
The above command stopped at the appropriate times and waited
for fresh tapes. The whole process took a little over an hour
and wrote 74525 tape blocks on 3 tape(s).
It is not perfectly clear how tightly the above command
packs the tapes. (Almost nothing was written on the third
tape).
I then reformatted the disk (to a 4.2 file system) and
attempted a restore via the "restore command". All appears
to have been properly restored ( I have not tryed
a "make world" command yet).
Conclusions:
All of the backup programs appear to be damaged to some
extent. Dump.bsd appears to be at least twice as fast
as tar and pax (but I could not get tar to function
properly for multiple tapes).
I wish Apple would make available the list of known problems
(and possible work arounds) for A/UX. How about a section
on support.aux.apple.com ( or is that aux.support.apple.com)
Appendix:
I tryed backing up my root partition (92 meg) with ExpressTape v4.1.
This program failed 3 times with 3 different sets of tapes. Apple's
HD Backup program WAS able to do the backup.( I have not
tried a restore...My distribution media was defective and
Apple loaded A/UX for me, I am starting the seventh week
of waiting for a replacement). In ExpressTapes defense let
me add that it did a fine job of a "files" backup of my
60 meg Mac Partition. Only took a little over an hour to
do the backup. This is MUCH faster that the Apple Backup
program in file by file backup.
That's the story the way I see it.
Jerry
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| Jerry LeVan | Phone:(606)-622-1931 |
| Department of Computer Science | |
| Eastern Kentucky University | Email:matlevan@eku.bitnet |
| Richmond Ky 40475 | |
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| "The series converges so slowly that it actually diverges." |
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