I'm following the Device Drivers, Features and Commands November 2008 manual for utilizing mainframe type tape drives.
I'm using escon attached IBM 3590 drives. All that stuff seems to work well, except when I try to turn on/off compression. Per the manual: To control Improved Data Recording Capability (IDRC) compression, use the mt command provided by the RPM mt-st. Compression is off after the tape device driver has loaded. To switch compression on, issue: # mt -f <node> compression or # mt -f <node> compression 1 where <node> is the device node for a character device, for example, /dev/ntibm0. To switch compression off, issue: # mt -f <tape> compression 0 Any other numeric value has no effect, and any other argument switches compression off. However, when I try to do it: linux64:/home/oracle # lstape TapeNo BusID CuType/Model DevType/Model BlkSize State Op MedState 0 0.0.05b1 3590/50 3590/11 auto UNUSED --- LOADED linux64:/home/oracle # mt -f /dev/ntibm0 compression 1 mt: invalid argument `compression' for `tape operation' linux64:/home/oracle # I didn't load a new driver in. I'm using just what came with SLES 10 SP2 and what gets installed with a default "more or less" installation. What makes me think the output isn't being compressed, which is the default for 3590s, is that Ditto reports: File 00002 has 12441600 bytes in 1215 blks, min blk=10240, max blk=10240 - compression ratio is 1:1 A compression ratio of 1:1 doesn't look like much compression is happening. My tar command didn't specify software compression so it's not a case of compressing a compressed file: linux64:/home/oracle # tar -cvf /dev/ntibm0 az*.* At this point, I don't need the capacity of compression, as my use should be under 10 GB native capacity of the tape. But I would like to find out what is missing... Thanks Tom Duerbusch THD Consulting ---------------------------------------------------------------------- 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
