On Friday 30 September 2005 08:10, [EMAIL PROTECTED] wrote: >Hi Listers, > >Just to give my 0.02EUR > >> > mt -f /dev/nst0 defcompression off (or 0 depending on your mt) >> > mt -f /dev/nst0 compression off (or 0 depending on your mt) > >I am running SuSE 9.3 and the only available mt operation is >"datcompression" > >See: >athene:~ # mt --version >GNU mt version 2.5 >athene:~ # man mt >[...] > datcompression > (some SCSI-2 DAT tapes) Inquire or set the compression >status > (on/off). If the count is one the compression status is >printed. > If the count is zero, compression is disabled. > Otherwise, com- > pression is enabled. The command uses the SCSI ioctl to > read and > write the Data Compression Characteristics mode page > (15). ONLY > ROOT CAN USE THIS COMMAND. > > >And in fact I do have the problem that I use at one site the Tandberg > SLR7 without knowing how to switch off hw-compression. The mt > datcompression {off|0} operation fails. That leads to my amanda.conf: > >define tapetype SLR7 { > comment "just produced by tapetype prog (hardware compression on)" > length 16500 mbytes # Manually decreased again > filemark 186 kbytes > speed 1300 kps >} > >athene:~ # dmesg | grep SLR > Vendor: TANDBERG Model: SLR7 Rev: 0483 > Type: Sequential-Access ANSI SCSI revision: 02 >Attached scsi tape st0 at scsi0, channel 0, id 3, lun 0 >st0: try direct i/o: yes (alignment 512 B), max page reachable by HBA >1048575 > > >BTW: Is it true that a tape formerly written with hw-compression will >"override" the 'drive compression off setting' because the compression >on/off status has been written on the header of the tape? If yes, I > should "reformat" a lot of tapes as described by Gene :-/ > > >Best regards >Uwe
I believe thats pretty much the universal case, Uwe. Think about it... Otherwise, how would the drive ascertain if the tapes data needed to be run thru the hardware decompression to make it valid data? The only other 'by the tape' method of defining it would be a slider button on the tape. But that could be moved by accident, so if I were designing such a device, I'd 'simplicate' that option out of the design before it ever hit the production line. But thats just the Old Farts thinking, based on 57 years of steering electrons for a living. I'll be 71 next week. -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) 99.35% setiathome rank, not too shabby for a WV hillbilly Yahoo.com and AOL/TW attorneys please note, additions to the above message by Gene Heskett are: Copyright 2005 by Maurice Eugene Heskett, all rights reserved.