Date: Thu, 27 May 1999 10:11:18 -0700 (PDT) From: Matthew Jacob <mjacob@feral.com> To: Dirk-Willem van Gulik <dirkx@webweaving.org>, Darryl Okahata <darrylo@sr.hp.com>, Karl Denninger <karl@Denninger.Net> Cc: freebsd-scsi@freebsd.org Subject: OnStream SCSI drives Message-ID: <Pine.BSF.4.05.9905271000550.64523-100000@semuta.feral.com> In-Reply-To: <Pine.BSF.4.05.9905251235340.360-100000@brunte.ispra.webweaving.org>
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I got the documentation for this device and got a drive unit, and took a quick look at this today (I have to be gone until next tuesday- my flight leaves in a couple of hours). The support for this is going to be quite complex. Not only is it the various modifications to commands (must have 'immediate' bit set, etc..), but it means that: + All records are 32KBytes user data *PLUS* a 512 byte AUX field that describes this tape frame. The AUX field has to not only describe what's in this record but also record the number of filemark frames preceeding this, etc... + Write errors due to defective media have to be handled in software- i.e., the data relocated to the next frame, with possibly updating the failed frame so that later read of that frame knows that it's bogus (and where to go for the 'good' frame). It will be possible to support variable mode or different blocksizes with this tape format- if we want to. Basically we have to do in software that which the Tandberg QIC tape devices do (and do in somwhat pixielike manner at that..). In any case, this is not a no-brainer trivial task. I'll start tackling it next week, but it'll probably take a couple of weeks at least. I'll ask Onstream if they mind the information going out so if others have more aggressive schedules they can try to implement this sooner if they lke, but you'd better coordinate with me on this. -matt To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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