SUMMARY: How to duplicate a tape?

From: A. Mahendra Rajah, Systems Manager <A.Mahendra.Rajah_at_Meena.CC.URegina.CA>
Date: Tue, 09 Feb 1999 09:47:16 -0600 (CST)

   I was trying to duplicate the contents of a DLT tape to another using
   two tape drives and the `dd' command which would copy the first file
   OK, but wouldn't correctly copy the rest. The command I used was:

   dd if=/dev/nrmt1h of=/dev/nrmt0h skip=1 files=10 bs=61440 conv=notrunc

   Thanks to the following for replying to my query:

        alan_at_nabeth.cxo.dec.com
        Kevin Reardon <kreardon_at_na.astro.it>
        John Francini <francini_at_nashua.progress.com>
        "Dr. Tom Blinn, 603-884-0646" <tpb_at_doctor.zk3.dec.com>
        Ian Goodacre <Ian.Goodacre_at_mbs.gov.on.ca>
        Lars Bro <lbr_at_dksin.dk>
        "Thomas.Meyer" <meyert_at_dla-marbach.de>
        tsh_at_mrc-lmb.cam.ac.uk (T. S. Horsnell)
        "C.J.Bol" <bol_at_Axp1.IenD.wau.nl>
        Mervyn Weis <Mervyn.Weis_at_digital.com>

   They suggested two options:

   (1) Use `dd' repeatedly for EACH file on the master tape, or
   (2) Use `tcopy'.

   I used `tcopy' since it was the easiest.

   The original replies are attached.

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From: alan_at_nabeth.cxo.dec.com


        Why are you using the skip=? That causes it to skip records,
        which is either applied to the first file of the tape or
        every file of the tape (I don't know which). If every
        file that easily explains why you have the problem; you
        haven't copied all the data. If it only applies to the
        pseudo-label, then I'm not sure what would happen. One
        thing you could do is pick a small vdump from the set,
        pull it off both tapes to disk and see how they differ.

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From: Kevin Reardon <kreardon_at_na.astro.it>

Mahendra,

Have you tried using the command tcopy? As in "tcopy /dev/nrmt1h
/dev/nrmt0h". See "man tcopy" for more information.

hope it helps,
kevin reardon

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From: John Francini <francini_at_nashua.progress.com>

A couple of things here...

"skip=1" says to skip one record, not one file, at least according to the dd
man page.

I think you may have to actually make a script that skips a file (using mt
rather than dd to do the skip), then loops 10 times doing:

        dd to read a file and write it to the second tape
        mt eof (to write an end-of-file mark, since I think dd is too dumb
                to do so)

At the end of the whole set of 10, use mt eof a second time to write a logical
EOT (two or more tape marks in a row).

Of course, all this is done with the norewind device names.

If someone else comes up with a more elegant solution, I'd be pleased to be
corrected!

Thanks,

John

-- 
John Francini, francini_at_progress.com
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From: "Dr. Tom Blinn, 603-884-0646" <tpb_at_doctor.zk3.dec.com>
You seem to be assuming that when you use "dd" with the "files=" option, it
copies each input file to a separate output file.  I suspect it appends all 
of the input files into a single output file.
I believe you need to use a separate "skip=" for each input file, and copy
one input file at a time to the output.  You could probably write your own
program that would do this more efficiently.  Or just start by using "mt" to
skip over the first file, then run "dd" once for each file to be copied, but
don't ask it to copy multiple files, and don't tell it to skip anything.  If
you have the /dev/nrmt on the input and output, it should just copy one file
from the input to one file in the output, and never reposition the tape in
between the steps.
Tom
 
 Dr. Thomas P. Blinn + UNIX Software Group + Compaq Computer Corporation
  110 Spit Brook Road, MS ZKO3-2/U20   Nashua, New Hampshire 03062-2698
   Technology Partnership Engineering           Phone:  (603) 884-0646
    Internet: tpb_at_zk3.dec.com           Digital's Easynet: alpha::tpb
     ACM Member: tpblinn_at_acm.org         PC_at_Home: tom_at_felines.mv.net
  Opinions expressed herein are my own, and do not necessarily represent
  those of my employer or anyone else, living or dead, real or imagined.
 
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From: Ian Goodacre <Ian.Goodacre_at_mbs.gov.on.ca>
Not sure about the skip and files arguments.
You might try:
mt -f /dev/nrmt1h rewind
mt -f /dev/nrmt1h fsf 1
dd if=3D/dev/nrmt1h of=3D/dev/nrmt0h bs=3D61440
dd if=3D/dev/nrmt1h of=3D/dev/nrmt0h bs=3D61440
dd if=3D/dev/nrmt1h of=3D/dev/nrmt0h bs=3D61440
...
Perhaps a bit crude, but it might work.
Ian Goodacre
Computer and Telecommunication Services (CTS)
Management Board Secretariat
155 University Avenue, 8th floor
Toronto, Ontario, M5H 3B7
Tel: 416-327-1092
Fax: 416-327-3281
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From: Lars Bro <lbr_at_dksin.dk>
Well, it simply must work....
You will need to run dd repeatedly once for each file,
DEV_1=/dev/nrmt1h
DEV_2=/dev/nrmt2h
while dd if=DEV_1 of=DEV_2
do
	true
done
What puzzles me is that you manually write and end-of-file marker at end
of the 
first tar(a marker comes when 1st tar closes). I never did that, maybe
you got this:
                                         dummy_tar EOF EOF 1st vdump EOF
2nd vdump
                                                      ^
                                                      |
                                                      |
And this is what you try to read with mt fsf 1 -------*
yours,
Lars Bro
   Lars Bro                                        lbr_at_dksin.dk
   ABB Daimler-Benz Transportation Signal A/S      +45 36 39 01 77
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From: "Thomas.Meyer" <meyert_at_dla-marbach.de>
Dear Mr. Rajah,
you might try the "tcopy" command (see man-page). It does a complete copy from
one tape to another.
Regards,
        Thomas Meyer, EDV-Systemadministrator
          email: Thomas.Meyer_at_dla-marbach.de
          smail: Deutsches Literaturarchiv Marbach
                 Schillerhoehe 8-10
                 D-71672 Marbach
        Telefon: +49-7144-848-141
            Fax:          ...-387
            WWW: http://www.dla-marbach.de
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From: tsh_at_mrc-lmb.cam.ac.uk (T. S. Horsnell)
Tried tcopy?
Cheers,
Terry.
Terry Horsnell (tsh_at_mrc-lmb.cam.ac.uk)
Computer Manager
Medical Research Council
Lab of Molecular Biology
Hills Road
CAMBRIDGE CB2 2QH
U.K.
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From: "C.J.Bol" <bol_at_Axp1.IenD.wau.nl>
mahendra, there is a 'tcopy'-program in Digital Unix.
Regards, Kees Bol
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From: Mervyn Weis <Mervyn.Weis_at_digital.com>
Hello Mahendra,
I don't know if this will help, but have a look at the tcopy utility (# man
tcopy). You might have to do some tape manipulation with the mt command for
multiple vdump images as the tcopy utility "assumes that there are two tape
marks at the end of the source tape when copying or reading". Nonetheless,
it might be worth a try.
Hope this helps.
Good Luck and Regards,
Merv Weis
e-mail: Mervyn.Weis_at_compaq.com
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Received on Tue Feb 09 1999 - 16:08:26 NZDT