[nflug] tape drive problems (scsi)

[Cyber Source]

Hello All,
  I have been starting to use scsi tape drives at a couple locations for 
backups and have encountered the same intermittent type of troubles at 
both locations, which is why I think it's something in my setups and not 
the hardware. Here is my problem, I'll stick to one location as once I 
figure it out, will probably explain the other. I have not been able to 
get reliable consistent backups going to these tape drives, sometimes 
they work, more often they don't. I have an external DDS-3 with the 
following info result from an mt status;

[root at softbase ~]# mt status
SCSI 2 tape drive:
File number=0, block number=0, partition=0.
Tape block size 512 bytes. Density code 0x25 (DDS-3).
Soft error count since last status=0
General status bits on (41010000):
 BOT ONLINE IM_REP_EN

Now, I have a very rudimentary  script  as a cron like so ( I don't need 
sequential backups, etc. )

#!/bin/bash
mt erase
tar cvf /dev/st0 /Backup/Monday
mt rewind

Here is an error message from last nights (dmesg output)

st0: Error with sense data: <6>st0: Current: sense key: Medium Error
    Additional sense: Excessive write errors
st0: Error with sense data: <6>st0: Current: sense key: Hardware Error
    Additional sense: Internal target failure
Info fld=0x14
st0: Error with sense data: <6>st0: Current: sense key: Hardware Error
    Additional sense: Internal target failure
Info fld=0x1
st0: Error on write filemark.
st0: Error with sense data: <6>st0: Current: sense key: Hardware Error
    Additional sense: Internal target failure
st0: Error with sense data: <6>st0: Current: sense key: Hardware Error
    Additional sense: Internal target failure

NOTE: This is the first time I have seen anything calling Hardware 
Error. Now if I remove the st module and put it back in, I get this from 
dmesg;

st: Unloaded.
st: Version 20050830, fixed bufsize 32768, s/g segs 256
st 3:0:0:0: Attached scsi tape st0<4>st0: try direct i/o: yes (alignment 
512 B), max page reachable by HBA 1048575
st0: Block limits 1 - 16777215 bytes.

So, my question would be, do I need to set a block size in my script to 
make this more reliable? I have read the man page on mt (and st), lots 
of options but no examples (so many scsi options). Anyway, so I might 
save myself tons of trial and error, can anyone give me a clue? Thanks, 
Peter

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