Multiple volumes Backup

Этот (см. ниже) backup вешает намертво машину.
В чем может быть причина?

Tape: HP - DDS4

========= LOG messages ========================
kernel: st0: Block limits 1 - 16777215 bytes.
kernel: st0: Error with sense data: Deferred st09:00: sense key Medium Error
kernel: Additional sense indicates Sequential positioning error
kernel: st0: Error with sense data: Deferred st09:00: sense key Medium Error
kernel: Additional sense indicates Sequential positioning error
kernel: st0: Error on write filemark.
========== end of LOG messages ================


===== Скрипт 1 fullbackup.sh ======
#! /bin/sh

/sbin/dump -0uf /dev/st0 -F /usr/sbin/cassete_end.sh /opt
/bin/mt -f /dev/st0 offline

===== end of Скрипт 1 ======

===== Скрипт 2  cassete_end.sh ======
#! /bin/bash

/bin/mt -f /dev/st0 offline
#if [ $? = 0 ]; then

mail -s "Full backup" root@domain.ru <<EOF
Please enter next cassete into the tape device.
EOF

STATUS=
while test -z "$STATUS"
do
  STATUS=`/bin/mt -f /dev/nst0 status | tail -1 | grep ONLINE`
  sleep 30
done
exit 0
===== end of Скрипт 2 ======