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Date:      Fri, 29 Mar 2002 14:16:32 -0800
From:      Michael Smith <msmith@freebsd.org>
To:        "Kenneth D. Merry" <ken@kdm.org>
Cc:        Lukas Ertl <l.ertl@univie.ac.at>, freebsd-scsi@freebsd.org
Subject:   Re: ciss driver and tagged queuing 
Message-ID:  <200203292216.g2TMGWN01304@mass.dis.org>
In-Reply-To: Your message of "Fri, 29 Mar 2002 08:11:13 MST." <20020329081113.A28622@panzer.kdm.org> 

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> > da1 at ciss1 bus 0 target 0 lun 0
> > da1: <RAID 5 OK > Fixed Direct Access SCSI-0 device
> > da1: 135.168MB/s transfers
> > da1: 416780MB (853565580 512 byte sectors: 255H 32S/T 39067C)
> > da0 at ciss0 bus 0 target 0 lun 0
> > da0: <RAID 1 OK > Fixed Direct Access SCSI-0 device
> > da0: 135.168MB/s transfers
> > da0: 17359MB (35553120 512 byte sectors: 255H 32S/T 4357C)
> 
> The problem is that the inquiry data doesn't indicate that the arrays
> support tagged queueing, so you only get one tag at a time.

The arrays don't support tagged queueing, but they do support multiple 
outstanding commands.

I don't want to have to handle tags; I just want CAM to keep giving me 
commands until I ask it to stop. 8)

One other complication is that the limit on outstanding commands is 
per-adapter not per-array, so the automatic tag-backoff that CAM does 
won't work correctly under load.

Any suggestions on improved behaviour here would be welcome.

-- 
To announce that there must be no criticism of the president,
or that we are to stand by the president, right or wrong, is not
only unpatriotic and servile, but is morally treasonable to 
the American public.  - Theodore Roosevelt



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