Date: Tue, 27 Feb 1996 07:13:39 -0800 From: "Justin T. Gibbs" <gibbs@freefall.freebsd.org> To: se@zpr.uni-koeln.de (Stefan Esser) Cc: Dave Andersen <angio@aros.net>, questions@freebsd.org Subject: Re: Ncr scsi: overlapped commands attempted Message-ID: <199602271513.HAA25190@freefall.freebsd.org> In-Reply-To: Your message of "Tue, 27 Feb 1996 13:45:07 %2B0100." <199602271245.AA29271@Sysiphos>
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>} The only thing that comes to mind is that an untagged request >} sense command is pending when another tagged command is queued >} to the target. The aic7xxx driver never tagges request sense commands >} since the spec dictates that they must be untagged (and some drives >} choke on this) and it also gurantees that no other commands are posted >} to the target until the request sense completes successfully. > >Yes, I know about this, and teh NCR driver makes >sure that no tags are used with REQUEST SENSE >commands. Okay. >The HP drive problems are most likely caused by >several tagged START STOP UNIT commands being sent >to the drive. Most drives do the right thing (i.e. >ignore a start unit if the motor is running :), >but a few seem to perform a soft reset and don't >tolerate several of these commands being active >at a time. Hmmm. This problem again. >The GENERIC SCSI code calls scsi_start_unit() >whenever a raw disk partition is opened, and two >programs do several opens within a millisecond: >FSCK and DUMP. > >I've been thinking about sending only teh first >start unit to each LUN, but for now I think the >generic SCSI code should NOT issue them in the >first place for EACH open. I think we should only send a start unit during bus probe and in certain cases during error handling (unit not ready?). It sounds too dangerous to do it any more often. >Regards, STefan >-- > Stefan Esser, Zentrum fuer Paralleles Rechnen Tel: +49 221 4706021 > Universitaet zu Koeln, Weyertal 80, 50931 Koeln FAX: +49 221 4705160 > ============================================================================= >= > http://www.zpr.uni-koeln.de/~se <se@ZPR.Uni-Koeln.DE> -- Justin T. Gibbs =========================================== FreeBSD: Turning PCs into workstations ===========================================
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