lusgr@vax1.cc.lehigh.edu (Steve Roseman) (03/08/91)
Today's Trivia Question: How does AIX tell what kind of 1/4" cartridge is in the drive? The question may be trivial, but I wasted at least 2 hours with the problem. I grabbed 2 fresh 6150 (150MB) tapes from the box to backup my 3003 release. I then proceeded to waste about 2 hours trying to write on the first tape, but kept getting errors whenever I tried to write on /dev/rmt0. The errors were immediate, not write or media failures. I rebooted, powered everything off, nothing helped. Diagnostics passed with no problems. On a whim, I tried writing to /dev/rmt0.4 (low density), and it worked. Finally, I tried the second tape, and no problems at all. First tape again, rmt0.4 works, rmt0 doesn't. I then happened to notice that on the back of the failing tape, included in a mass of numbers it said 600A, and the good one said 6150. Ah, the manufacturer put the wrong label on the tape, so I complained, etc. So, how did AIX know? I can't see any differences in the cartridges, so I presume it has something to do with the little dance the tape does when put into the drive. The manufacturer's rep said by the tape oxide color, but I don't believe that. Thanks for any responses, Steve ------------------------------------------------------------------------- Steve Roseman Lehigh University Computing Center LUSGR@VAX1.CC.Lehigh.EDU
rudy@chukran.austin.ibm.com (03/08/91)
The way most that the IBM 1/4" tape unit tells what the density of tape is via holes punched in the tape. I suspect that all other units do the same, but they are less "picky" about what sort of tape they write on. For example , I took a quick look at a 3M DC600A tape just now, and as I moved the drive wheel by hand to move the tape forward, I saw 2 punched holes go by. These will pass by the angled mirror in the cartridge and be detected by the tape drive. This is also how end of tape is detected. If you examine a 6150 tape, you will find the pattern is different, but I havent taken the time to verify what the pattern is. The tape unit is not smart enough to know what the oxide coating is. In fact, I would guess the the 3M DC600A and DC6150 tapes come off the same manufacturing line since they are both rated for the same FTPI (12500 flux transitions per inch). The difference is the number of tracks written. QIC120 is 15 tracks, which can be written on either the 600A or the 6150. QIC 150 is 18 tracks and can only be written on a 6150. By the way, QIC 24 is 9 tracks at 10000 tpi, which can be read by this drive but not written. Also be aware that this drive is strange in that if you had written your QIC24 tape on a 600A tape, the drive will not read it, but if you had written your QIC24 tape on a 300XLP tape, then it will read it. This tape drive was manufactured for IBM by Tandberg. It has its own very peculiar personality that make it most unlike other popular QIC120/150 drives (like Archive and Cipher). THe default setting is to enable the ECC (error correcting code) when writing tapes. Tapes written with ECC on will not interchange with any other QIC 120/150 drive, so IBM recommends that you turn off ECC if you wish to interchange. In fact, IBM is recommending that you turn off ECC for good. A future software update will change the default setting to OFF. This feature has not worked well. ALso please be aware that this setting only applies to writing tapes. If you do have tapes that were written with ECC on, then the drive should read them, regardless of the setting. Trivia exercise for the reader: Report to the class what the sensing hole patterns are for 300XLP, 600A and 6150 tapes. ********************************************************************* IBM AIX Porting Center | RSCS: CHUKRAN at AUSTIN 11400 Burnet Rd. | AWDnet: rudy@chukran.austin.ibm.com Internal ZIP 2830 | internet: chukran@austin.iinus1.ibm.com Austin, Texas 78758 | Voice: 512-838-4674 Tieline: 678-4674 *********************************************************************
olson@newmedia.esd.sgi.com (Dave Olson) (03/09/91)
In <211.27d642c4@vax1.cc.lehigh.edu> lusgr@vax1.cc.lehigh.edu (Steve Roseman) writes: | How does AIX tell what kind of 1/4" cartridge is in the drive? | | The question may be trivial, but I wasted at least 2 hours with the problem. | I grabbed 2 fresh 6150 (150MB) tapes from the box to backup my 3003 release. | I then proceeded to waste about 2 hours trying to write on the first tape, but | kept getting errors whenever I tried to write on /dev/rmt0. The errors were | immediate, not write or media failures. I rebooted, powered everything off, | nothing helped. Diagnostics passed with no problems. On a whim, I tried | writing to /dev/rmt0.4 (low density), and it worked. Finally, I tried the | second tape, and no problems at all. First tape again, rmt0.4 works, rmt0 | doesn't. I then happened to notice that on the back of the failing tape, | included in a mass of numbers it said 600A, and the good one said 6150. Ah, | the manufacturer put the wrong label on the tape, so I complained, etc. The drive detects the difference by the hole pattern at BOT. It sounds like AIX didn't detect it (or at least report it with a unique error) at all. The drive itself will refuse to write the wrong type of tape (normally QIC24). Now the interesting thing is that QIC120 (i.e., 600A) tapes are normally writable on a QIC150 drive... So what is the scoop; is IBM using a QIC150 only drive, or are they programming the drive to run in only QIC150 mode?
afx@ibm.de (Andreas Siegert) (03/12/91)
olson@newmedia.esd.sgi.com (Dave Olson) writes: >The drive itself will refuse to write the wrong type of tape (normally >QIC24). Now the interesting thing is that QIC120 (i.e., 600A) tapes are >normally writable on a QIC150 drive... So what is the scoop; is IBM using >a QIC150 only drive, or are they programming the drive to run in only >QIC150 mode? When reading it does not matter, but when writing you have to specify the density with rmtx.Y where an Y >= 4 specifies QIC 120, else QIC 150 is assumed. -- Andreas Siegert IBM Deutschland GmbH Voice: +49 89 7670-509 AIX Field Support Center Pocci Strasse 11 Fax: +49 89 7670-555 siegert@ibm.de D-8000 Muenchen 2 All opinions expressed are my own and not an official IBM Statement!