Backup on DDS-4 tapes

[Ludo Koren]

Hi,

I am using 5.2.1-RELEASE-p3 for backup on DDS-4 tapes 40GB in size.

# df -k
Filesystem      1K-blocks     Used    Avail Capacity  Mounted on
/dev/vinum/root   1016162   157405   777465    17%    /
devfs                   1        1        0   100%    /dev
/dev/vinum/usr   84746248 54467390 23499160    70%    /usr
procfs                  4        4        0   100%    /proc
# camcontrol devlist -v
scbus0 on ahd0 bus 0:
<IBM IC35L018UWD210-0 S5BS>        at scbus0 target 3 lun 0 (pass0,da0)
<IBM IC35L073UWDY10-0 S25F>        at scbus0 target 9 lun 0 (pass1,da1)
<HP C5683A C005>                   at scbus0 target 10 lun 0 (sa0,pass2)
<  >                               at scbus0 target -1 lun -1 ()
scbus1 on ahd1 bus 0:
<IBM IC35L018UWD210-0 S5BS>        at scbus1 target 1 lun 0 (pass3,da2)
<IBM IC35L073UWDY10-0 S23C>        at scbus1 target 8 lun 0 (pass4,da3)
<  >                               at scbus1 target -1 lun -1 ()
scbus-1 on xpt0 bus 0:
<  >                               at scbus-1 target -1 lun -1 (xpt0)
# /sbin/dump -SLu0 -B 41943040 -C 32 -f /dev/sa0 /usr
  DUMP: Date of this level 0 dump: Mon Mar 14 10:29:51 2005
  DUMP: Date of last level 0 dump: the epoch
  DUMP: Dumping snapshot of /dev/vinum/usr (/usr) to /dev/sa0
  DUMP: mapping (Pass I) [regular files]
  DUMP: Cache 32 MB, blocksize = 65536
  DUMP: mapping (Pass II) [directories]
  DUMP: estimated 54189311 tape blocks on 1.29 tape(s).
# 
# mt -f /dev/sa0 status
Mode      Density              Blocksize      bpi      Compression
Current:  0x26:DDS-4           variable       97000    DCLZ
---------available modes---------
0:        0x26:DDS-4           variable       97000    DCLZ
1:        0x26:DDS-4           variable       97000    DCLZ
2:        0x26:DDS-4           variable       97000    DCLZ
3:        0x26:DDS-4           variable       97000    DCLZ
---------------------------------
Current Driver State: at rest.
---------------------------------
File Number: 0  Record Number: 0 Residual Count 0

I am using the following command:

# /sbin/dump -Lu0 -B 41943040 -C 32 -f /dev/sa0 /usr

or 

# /sbin/dump -aLu0  -C 32 -f /dev/sa0 /usr

Why I cannot dump the filesystem on 2 tapes (it takes 3, it seems it
works without compression) no matter if I use dump or cpio? What I am
doing wrong?

Any hints appreciated. Thank you very much in advance.

Regards,

lk