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Date:      Thu, 25 Aug 2011 14:24:57 -0400
From:      Renee Gehlbach <fbsd-ml@gehlbach.com>
To:        questions@freebsd.org
Subject:   Problem reading from tape drive
Message-ID:  <4E569379.4070005@gehlbach.com>

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I recently purchased a FreeBSD-compatible SAS card (an Adaptec ASR 
2045)  and moved our backup server from Ubuntu to FreeBSD 8.2.  I am 
trying to set up the backup software, but am having problems with the 
tape drive.  Hopefully this is a "duh" type question, since I have a lot 
more experience working with tape drives in Ubuntu than FreeBSD.

I installed bacula, and ran the test function in the btape utility.  It 
wrote 10000 blocks, wrote EOF, wrote 10000 blocks, wrote EOF, wrote 
EOF.  Rewound the tape.  Read 10000 blocks, failed reading the second 
10000 blocks.  I had no luck researching the bacula error message, so I 
switched to mt and tar for further troubleshooting.

camcontrol devlist does show the tape drive:
backup# camcontrol devlist
<QUANTUM ULTRIUM 3 2182>           at scbus2 target 0 lun 0 (sa0,pass0)


So then I went into a directory that had one subdirectory, which 
contained several plain text logfiles.  I did four tars, alternating 
between that directory and the subdirectory (so I would be able to see a 
difference between the tar files).

backup# mt -f /dev/nsa0 rewind
backup# tar -cf /dev/nsa0 *
backup# cd log/
backup# tar -cf /dev/nsa0 *
backup# cd ..
backup# tar -cf /dev/nsa0 *
backup# cd log/
backup# tar -cf /dev/nsa0 *


So far so good.  Then I went back to read those tar files.

backup# mt -f /dev/nsa0 rewind
backup# tar -tf /dev/nsa0
log/
log/mbw01.log
(....insert rest of correct tar listing)
backup# tar -tf /dev/nsa0
tar: Unrecognized archive format
tar: Error exit delayed from previous errors.


So....same results as bacula's tape test utility was giving.....it 
writes, it reads the first file, then errors on trying to read the 
second file.  However:


backup# mt -f /dev/nsa0 rewind
backup# tar -tf /dev/nsa0
log/
log/mbw01.log
(....insert rest of correct tar listing)
backup# mt -f /dev/nsa0 fsf
backup# tar -tf /dev/nsa0
mbw01.log
(....insert rest of correct tar listing)
backup# mt -f /dev/nsa0 fsf
backup# tar -tf /dev/nsa0
log/
log/mbw01.log
(....insert rest of correct tar listing)
backup# mt -f /dev/nsa0 fsf
backup# tar -tf /dev/nsa0
mbw01.log
(....insert rest of correct tar listing)
backup# mt -f /dev/nsa0 fsf


So, when I tell it to forward space file at the end of each tar file, it 
is able to read all four files correctly.  This leaves me scratching my 
head, and wondering what the heck I've set up wrong.  Any ideas?

Thanks,
Renee Gehlbach



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