Hardware compression

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There are multiple methods to set (turn off) hardware compression.

  • Using stinit command: stinit(8) command initializes the SCSI tape drives at the system startup by sending driver ioctl commands. Use "comp" field in /etc/stinit.def configuration file to configure hardware compression for each type of tape.
  • Use mt(1) command to turn off hardware compression at boot time. For example:
# mt -f /dev/st0 compression 0

Please note that compression information is not stored on the tapes ident header block until the tape has been written to.

Procedure for turning off compression and labelling tapes

  • Label the tape
  • Rewind the tape
  • Read the label to a file using dd command
  • Turn off tape compression using mt(1) command. See above.
  • Re-write the label block and write more /dev/zero blocks to flush its buffers.
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