It was clarified that hw compression feature of our 3592 tape system is
selectable by the applications/operating systems, so this was not the
reason for "mt datcompression" to fail.
I then tried mtst; it seems to work:
zlnx006:~ # vmcp att 500 '*'
zlnx006:~ # chccwdev -e 500
zlnx006:~ # mtst -f /dev/ntibm0 compression 1
zlnx006:~ # mtst -f /dev/ntibm0 compression 0
"mtst compression" doesn't return any information on the terminal, but
it seems that the tape driver writes kern.warn messages to syslog, so
results of the previous commands can be seen in console and in
/var/log/messages:
Jun 3 16:13:46 zlnx006 kernel: TAPE_CORE: tape device 0.0.0500 found
Jun 3 16:13:54 zlnx006 kernel: TAPE_CORE: (0.0.0500): Tape is unloaded
Jun 3 16:13:54 zlnx006 kernel: TAPE_BLOCK: Detecting media size...
Jun 3 16:13:54 zlnx006 kernel: TAPE_3590: (0.0.0500): Tape operation
when medium not loaded
Jun 3 16:14:49 zlnx006 kernel: TAPE_CORE: (0.0.0500): Tape has been mounted
Jun 3 16:16:55 zlnx006 kernel: TAPE_STD: (0.0.0500) Compression is
currently on
Jun 3 16:16:55 zlnx006 kernel: TAPE_STD: Use 1 to switch compression
on, 0 to switch it off
Jun 3 16:17:16 zlnx006 kernel: TAPE_STD: (0.0.0500) Compression is
currently off
Jun 3 16:17:16 zlnx006 kernel: TAPE_STD: Use 1 to switch compression
on, 0 to switch it off
So it seems that the Device Drivers document really means mtst command
when it says mt.
For this, I propose an improvement for s390-tools sw: it would be nice
to see current compression status of a tape device e.g. in lstape
output. (At least I did not figure out how to see the status with the
general mtst tool.)
Regards,
Juha
Carsten Otte wrote:
Juha Vuori wrote:
I understand that there should be a compression feature inside this tape
system.
According to Device Drivers, Features, and Commands - SC33-8289-04, it
could be activated in tape_3590 driver with
# mt -f /dev/rtibm0 compression 1
but "mt" in this distribution does not support "compression" command.
I've looked at the mt in my fedora installation, and it does'nt have
compression as well. You need something that ends up calling this one
[from /usr/include/linux/mtio.h]:
#define MTCOMPRESSION 32/* control compression with SCSI mode page 15 */
According to gnu.org, gnu mt does'nt support this call at all:
http://www.gnu.org/software/tar/manual/html_node/mt.html
You need to have the mt-st tool, which is an extended version of mt.
Try to install the mt-st rpm that comes with your distribution, it
should support --compression as stated above. Looks like we need to
update the documentation there.
so long,
Carsten
----------------------------------------------------------------------
For LINUX-390 subscribe / signoff / archive access instructions,
send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or
visit
http://www.marist.edu/htbin/wlvindex?LINUX-390
----------------------------------------------------------------------
For LINUX-390 subscribe / signoff / archive access instructions,
send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit
http://www.marist.edu/htbin/wlvindex?LINUX-390
