From owner-freebsd-scsi@FreeBSD.ORG  Tue Mar 15 15:22:35 2005
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Date: Tue, 15 Mar 2005 09:22:19 -0600
From: Dan Nelson <dnelson@allantgroup.com>
To: Scott Long <scottl@samsco.org>
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Subject: Re: iSCSI initiator driver beta version, testers wanted
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In the last episode (Mar 15), Scott Long said:
> Danny Braniss wrote:
> >things are looking much better 2day, got tag queuing to work, and
> >now it's much faster. Q: how can the driver tell the cam to enable
> >queing (ie: camcontrol tag 0:0:0 -Nn), and
> 
> case XPT_PATH_INQ:
> 	cpi->hba_inquiry = PI_TAG_ABLE
> 
> >Q: is there a rule of thumb as to how many tag'ed?
> 
> When you call cam_sim_alloc(), there are arguments for how many
> concurrent tagged and untagged transactions the driver can handle. I
> don't know how tags work in iscsi, so I can't say what a good number
> is here.  Note that tag management is left completely up to the
> driver; CAM will tell you whether or not to use a tag for a
> particular CCB, but it's up to the driver to assign and track the tag
> number.

I would guess that tags would be even more useful for iscsi than
direct-attached scsi, due to the extra latency.  The more the better.

-- 
	Dan Nelson
	dnelson@allantgroup.com