Red Hat Bugzilla – Bug 9915
tar and dd report I/O Error on SCSI Tape while mt seems to work
Last modified: 2008-05-01 11:37:54 EDT
We use a SCSI tape (DDS-3) on a Netfinity 5500-M20 running RedHat Linux V
Operations like "mt rewind" and "mt erase" seem to work (At least they
report no error and the tape drive is doing something.). But "dd if=xxx
of=/dev/st0 bs=512" comes up with an I/O Error. I tried "dd if=/dev/zero
of=/dev/nst0 bs=512 count=1" and it reported no error which indicates that
it is not a HW problem.
"tar -c -v -b 1 -f /dev/st0 xxx" reports no error. But when I try to read
the tape afterwards with "tar -t -v -b 1 -f /dev/st0" it comes up with
"Doesn't look like a tar archive ... skipping to next file header".
I tried the above commands with different block size but the result was the
same. We have a second Netfinity 5500 (no M20) with the same SCSI tape
drive but running DLD Linux 6.0. And there all these command run without
any problem in production since 1 1/2 year.
We exchanged the tape with another one from a different vendor but the
behaviour is the same. mt status, mt rewind and mt retension work fine.
But mt setblk xxx, tar and dd report /dev/st0 I/O-Error.
All of status/retension/rewind do not read data from the media, while
tar/dd do, so the behavior is consistent.
Are there error messages in /var/log/messages?
Is there *any* tape that can be read by the drive?
Is there any tape that can be *written* by the drive?
dd if=xxx of=/dev/st0
/var/log/messages has an entry
Mar 10 14:50:17 altair kernel: st0: Write not multiple of tape block size.
Mar 10 14:51:17 altair last message repeated 2 times
I checked with different blocksizes: (bs=0, bs=1, bs=64, bs=512, bs=1024) but it
is all the same.
tar cfv /dev/st0 xxx
there is no entry in /var/log/messages. But if I issue afterwards
tar tfv /dev/st0
the tar command responds with
tar: Hmm, das sieht nicht wie ein ;tar+-Archiv aus.
tar: Springe zum Kopfteil der ndchsten Datei.
. Translation: Doesn't look like a tar archive. Jumping to next File.
We tried to write with different tapes (but all same vendor/type). But the
result was the same. We have the same type of tape also in another Netfinity
5500 (no M20) running DLD Linux and it works fine since nearly 1 1/2 years.
Regarding reading tapes: Though we have a tape device that works in another
Netfinity 5500 I cannot change the backup procedures there and I have no access
to that tape device or the tapes. This server is running in production and I am
not allowed to use it for some test purposes.
Stuff like cabling and termination an external HW support company and myself
We installed an Adaptec SCSI controller in addition and attached the tape
device to it. Now we can work with the tape device.
Though this is a workaround and not a fix it solves our issue to work with the
tape device. So we will not continue to firther investigate and the request is
closed from our side.
I believe the culprit is the ServeRAID driver not handling tape drives. We
added a Adaptec SCSI adapter, as well, based on the last posting here. That
works fine. The only difference was the adapter/driver.
Hope this helps.