tar backup on tape doesn't work

[Budiono]

Hi all,
I 'm just install a scsi card BusLogic BT-958 and HP DAT 40, on my 
fedora core 6 system. I usually backup my system, using tar.
My problem is backup doesn't running well.

And this is my backup script:
#tar -b 1024 -cvf /dev/st0 /usr/local/src/my_home/yahoomail | bzip2 -9 > 
/var/log/Backup.log.bz2

Backup only run a while, and archive some files in directory and then stop.

[root@mis-s155 ~]# tar -b 1024 -cvf /dev/st0 
/usr/local/src/my_home/yahoomail | bzip2 -9 > /var/tmp/Backup.log.bz2
tar: Removing leading `/' from member names
tar: /dev/st0: Cannot write: Device or resource busy
tar: Error is not recoverable: exiting now



But when I put out -b parameter on tar.  It run a while and not backup 
directory at all

The backup script I used was running well when I'm using redhat 9.0 system.
I attach some message from my system

scsi: ***** BusLogic SCSI Driver Version 2.1.16 of 18 July 2002 *****
scsi: Copyright 1995-1998 by Leonard N. Zubkoff <lnz(a)dandelion.com&gt;
scsi5: Configuring BusLogic Model BT-958 PCI Wide Ultra SCSI Host Adapter
scsi5:   Firmware Version: 5.06I, I/O Address: 0xDC00, IRQ Channel: 
225/Level
scsi5:   PCI Bus: 2, Device: 3, Address: 0xFEAFF000, Host Adapter SCSI ID: 7
scsi5:   Parity Checking: Enabled, Extended Translation: Enabled
scsi5:   Synchronous Negotiation: Fast, Wide Negotiation: Enabled
scsi5:   Disconnect/Reconnect: Enabled, Tagged Queuing: Enabled
scsi5:   Scatter/Gather Limit: 128 of 8192 segments, Mailboxes: 211
scsi5:   Driver Queue Depth: 211, Host Adapter Queue Depth: 192
scsi5:   Tagged Queue Depth: Automatic, Untagged Queue Depth: 3
scsi5:   SCSI Bus Termination: Both Enabled, SCAM: Disabled
scsi5: *** BusLogic BT-958 Initialized Successfully ***
scsi5 : BusLogic BT-958
  Vendor: HP        Model: C5683A            Rev: YP61
  Type:   Sequential-Access                  ANSI SCSI revision: 03
scsi 5:0:3:0: Attached scsi generic sg1 type 1
st: Version 20050830, fixed bufsize 32768, s/g segs 256
st 5:0:3:0: Attached scsi tape st0
st0: try direct i/o: yes (alignment 512 B)


[root@mis-s155 ~]# mt -f /dev/st0 status
SCSI 2 tape drive:
File number=-1, block number=-1, partition=0.
Tape block size 0 bytes. Density code 0x26 (DDS-4 or QIC-4GB).
Soft error count since last status=0
General status bits on (1010000):
 ONLINE IM_REP_EN

I very appeciate for any solution and comment.

Thank you
Budiono