Date: Mon, 15 Jan 2001 09:37:57 -0700 (MST) From: Eric Lee Green <eric@estinc.com> To: Jean-Francois Dockes <jean-francois.dockes@wanadoo.fr> Cc: mjacob@feral.com, freebsd-scsi@FreeBSD.ORG Subject: Re: Why filemarks in sardpos? Message-ID: <Pine.LNX.4.21.0101150910020.882-100000@h23.estsatnet> In-Reply-To: <14946.48266.332620.887204@hautmedoc.dockes.com>
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On Mon, 15 Jan 2001, Jean-Francois Dockes wrote: > So, yes, I have an opinion, and it is that no flush should be performed. In > practise, I think that only the 'First Block' value is useful for backup > software, and its signification is pretty clear. I guess that the comment > in the code about how the SCSI spec is vague relate to the 'Last block' > value, but I can't really understand what the 'Last Block' thing is good > for anyway. Well, I agree (obviously!). Sunday I decided to skip the whole tape driver and go straight to the sgen device that corresponds with the tape drive and issue raw SCSI commands to grab tape position (no, I'm not intermingling sgen and sa commands, this was for use from the storage manager prior to opening sa for read or write). I had the Tandberg SLR 50/60/100 manual and noticed that 'Last Block Location' is hard-coded to zero when you request logical block position (BT=0). Obviously this isn't too useful! I believe the Mammoth II also hardwires 'Last Block' to '0'. The Seagate DAT says it has something in the 'Last Block Location' field (apparently a copy of whatever is in the 'First Block Location' field, according to page 121 of the DDS-4 manual), but obviously if one of our major supported drives has it hard-coded to zero, this tends to indicate that the field is useless. -- Eric Lee Green eric@estinc.com Software Engineer "The BRU Guys" Enhanced Software Technologies, Inc. http://www.estinc.com/ (602) 470-1115 voice (602) 470-1116 fax To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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