Re: Connection Consensus Progress

[David Robinson <David.Robinson@EBay.Sun.COM>]

> I agree with you up to a point.  I know of customers that always need
> multiple physical paths to the Storage Controller.  Regardless of how fast
> the link is, they need a faster link, and these hosts need to be able to
> spread the load across several different HBAs.  (Some are on one PCI bus,
> and some on another, etc.)  When this happens, as it does today, with Fibre
> Channel, we are required, as are a number of other vendors, to come up with
> a multi HBA balancer.  We call our Fibre Channel version "DPO" (Dynamic
> Path Optimizer), EMC has another version (I do not know what they call
> theirs).  This Code sits as a "Wedge" Driver above the FC Device Drivers
> and balances the work across the different FC HBAs.  I think this same
> thing will be required in the iSCSI situation.  Note:I think, the FC
> versions only work with IBM or EMC's etc. Controllers.  (SUN probably has a
> similar one also.)

I understand this scenerio, it is often used as a high availability feature.
The key question is if this should be handled above at the SCSI layer
as it is most often done now, or in the iSCSI transport. While I like
the goal to unify this into one architecture, I have serious doubts that
we have the understanding of the requirements and needs necessary
to get it right.  Thus we will ultimately end up in the same situation
we are in today with a SCSI layer solution.  In addition, if the promise
of a hardware iSCSI NIC/HBA is acheived, allowing multiple paths using
different NIC/HBAs will still require "wedge" software.

	-David