Re: multiple connections

["Matt Wakeley" <matt_wakeley@agilent.com>]

Joshua Tseng wrote:

> >One downside I see to this proposal is that for a host with multiple iSCSI
> >nics, it will have to issue two commands (in this order): one to the "data
> path
> >nic" to describe where the data is to be read from/written to, and one to
> the
> >"control path nic" to send the command.  This would be communication to two
> >cards instead of one.  Also, note that the communication to the data path
> nic
> >MUST complete before the control path nic sends the command, requiring some
> >kind of sync mechanism.
>
> I don't understand why you think two commands are necessary.  A single
> commanddown the command/control connection will work.  This is my view of how
> an
> async model would work:

I'm sorry for the confusion.  When I said "two commands" I was referring to
whatever register read/write operations the host CPU would have to perform to
the NIC hardware itself to set up the intended SCSI I/O.  Not a command that
would be delivered to the target.

So, in my example, if the command is sent across NIC "A" and the data across NIC
"B", then the host will have to communicate to NIC "B" the scatter/gather list
information, as well as what to do with the SCSI status, then it will have to
communicate to NIC "A" to send the iSCSI command.  That's just that much more
control overhead that needs to be performed across the host's I/O busses.

-Matt