Date: Tue, 27 Nov 2001 08:33:14 -0500 From: Courtney Thomas <ccthomas@flash.net> To: Ted Mittelstaedt <tedm@toybox.placo.com> Cc: Anthony Atkielski <anthony@freebie.atkielski.com>, freebsd-questions@FreeBSD.ORG Subject: Re: SCSI tape back that works under FreeBSD Message-ID: <3C03961A.2060109@flash.net> References: <000101c17714$2abf0ea0$1401a8c0@tedm.placo.com>
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Ted Mittelstaedt wrote: >> -----Original Message----- >> From: Anthony Atkielski [mailto:anthony@freebie.atkielski.com] >> Sent: Monday, November 26, 2001 3:55 AM >> To: Ted Mittelstaedt >> Cc: freebsd-questions@FreeBSD.ORG >> Subject: Re: SCSI tape back that works under FreeBSD >> >> >> Ted writes: >> >> >>> Heli-scan technology was a good thing when it came >>> out, but today there's DLT which is much better in >>> terms of reliability in a production environment. >> >> I'd use DLT if it didn't cost four times as much as DAT for both drives and >> media. With the light use I give my drive, and the fact that the >> drive reading >> the tape is always the same drive that wrote it, I hope not to have >> any problems >> any time soon. >> > > I myself use DAT at home, light duty, and have had no problems. I mainly > wanted > to emphasize that while DAT is fine for light use, it won't stand up to a tape > cassette's worth of data totally rewritten every night for a year. You have > to > be a little careful when recommending solutions to note the environment they > work in. > > >>> When that figure starts to rise then get the tape >>> drive realigned before you start tossing tapes. >> >> Is realignment any cheaper than just buying a new drive? >> > > It depends on the drive - on the Exabyte 8mm drives it certainly was. On the > others, not so much. > > But there's another reason to do periodic alignmnets - hardware compression. > > DAT tape is pretty interchangeable from manufacturer's drive to manufacturer's > drive as long as the drive's hardware compression is switched off. But if > it's turned on, some drives use compression schemes that other's can't read. > > It would suck mightily if you had 3 years of backup tape saved up, all > hardware > compressed, and you replaced the tape drive and found all old tapes to be > unreadable. > > > Ted Mittelstaedt tedm@toybox.placo.com > Author of: The FreeBSD Corporate Networker's Guide > Book website: http://www.freebsd-corp-net-guide.com > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-questions" in the body of the message > > 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
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