Date: Wed, 28 Nov 2001 09:10:17 -0600 From: Bob Willcox <bob@immure.com> To: Courtney Thomas <ccthomas@flash.net> Cc: Ted Mittelstaedt <tedm@toybox.placo.com>, Anthony Atkielski <anthony@freebie.atkielski.com>, freebsd-questions@FreeBSD.ORG Subject: Re: SCSI tape back that works under FreeBSD Message-ID: <20011128091017.A89511@luke.immure.com> In-Reply-To: <3C03961A.2060109@flash.net>; from ccthomas@flash.net on Tue, Nov 27, 2001 at 08:33:14AM -0500 References: <000101c17714$2abf0ea0$1401a8c0@tedm.placo.com> <3C03961A.2060109@flash.net>
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I've used Exabyte 8mm drives for years on FreeBSD (as well as some other OSes) and haven't had streaming problems with them so long as I make certain that they are either set to a large blocksize or better yet, to variable blocksize. If you have the drive set to a small fixed blocksize it won't stream (on input or output). You can check/set this with the mt command. For example with my drive I get: $ mt status Mode Density Blocksize bpi Compression Current: 0x27:Mammoth variable 77611 IDRC ---------available modes--------- 0: 0x27:Mammoth variable 77611 IDRC 1: 0x27:Mammoth variable 77611 IDRC 2: 0x27:Mammoth variable 77611 IDRC 3: 0x27:Mammoth variable 77611 IDRC --------------------------------- Current Driver State: at rest. --------------------------------- File Number: 44 Record Number: 0 Residual Count 0 with mt and as you can see the blocksize is variable. Also, I never bother with programs such as buffer or team as I find that dump does a good job of buffering its output for the tape drive. One further note: In my experience the newer Mammoth Exabyte drives (I haven't tried a Mammoth2 yet) are _much_ better than all of the other 8mm and 4mm drives that I have used. These have a higher capacity (a native capacity of 20GB for Mammoth and 60GB for Mammoth2), higher data rates (3MB/s for Mammoth and I believe about double that for Mammoth2), and, in my experience, have been significantly more reliable. Unlike the older Exabyte drives (which were modified Sony VCR transports as I understand it), these drives have no capstans or pinch rollers and move the tape faster and with less stress/wear. Bob On Tue, Nov 27, 2001 at 08:33:14AM -0500, Courtney Thomas wrote: > > Speaking of Exabyte drives, I [am trying to :-)]use the 8500 [no > compression] but.............. > can't get it to stream, after trying many permutations [and a couple of > days] of possible commands. > > I've also erased the [new] tape, cleaned the drive with an Exabyte > cleaning cartridge, changed the cable, etc. > > BTW, an Athlon 750mhz w/256MB ram, AHA1520 card. I realize this is a low > end card but it has worked in another machine OK. The drive is almost > unused since new and appears to work satisfactorily other than no streaming. > > I've read the dump, st, and buffer man pages and the st page in > particular documents the driver functionality in extremis [for only a > user :-)] nevertheless it is clear that there are many, many > potentially troublesome variables that it seems to me only a proficient > C programmer with lots of time and a real good working knowledge of > things SCSI could probe. > > The command I'm using is............... > dump 0ub 64 /<dir> | `buffer -s 16k > /dev/tape` > > Since you use a DAT at home and are familiar with [at least the Exabyte] > 8mm drives, hopefully you can point me to a resolution. > > Also, since this is a discontinued product, Exabyte is no help, now, > though they were vigorously supportive when I first got the drive. > > Hopefully, > > Courtney Thomas > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-questions" in the body of the message -- Bob Willcox Boucher's Observation: bob@vieo.com He who blows his own horn always plays the music Austin, TX several octaves higher than originally written. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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