Date: Tue, 15 Mar 2005 09:22:19 -0600 From: Dan Nelson <dnelson@allantgroup.com> To: Scott Long <scottl@samsco.org> Cc: scsi@freebsd.org Subject: Re: iSCSI initiator driver beta version, testers wanted Message-ID: <20050315152219.GD67769@dan.emsphone.com> In-Reply-To: <4236E6AB.1060405@samsco.org> References: <E1DB70V-0005xD-5c@cs1.cs.huji.ac.il> <4236E6AB.1060405@samsco.org>
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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
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