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
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