Re: iSCSI Autosense Consensus, Connection next steps

[Stephen Bailey <steph@cs.uchicago.edu>]

> Second, on connections, I haven't seen enough discussion to call
> consensus, but I am going to try to narrow the option space and
> structure the discussion.  Four models for sessions have been
> proposed:
> 
> (1) Symmetric - all connections usable for command and data.
> (2) Asymmetric - single command connection, others are data.
> (3) Split - assign LUN sets to specific connections or pools of
> 	connections.
> (4) SCTP - use SCTP's support for multiple connections.

For the purposes of shaping the consensus, here's my stance:

  1) SCTP should only be pursued if TCP does not admit a viable
     solution to the iSCSI requirements.


Given that there are many iSCSI community participants expressing the
belief that iSCSI on TCP IS possible, I believe iSCSI on SCTP
proponents are just going to be stuck holding an `I told you so'
card.

This gates my second statement:

  2) multiple connections per session should only be supported if the
     underlying transport (e.g. SCTP) layer supports it.

Obviously, TCP does not presently support this abstraction, so
assuming SCTP gets killed for now, I am against multiple connections
per session.

In general, I am dubious that connection bundling above the transport
layer, but below some more application-informed layer (e.g. a wedge
driver) will work acceptably.  However, if the transport layer
provides it, then, by definition, it must work (ha, ha), or at least
it's not iSCSI's place to say that it won't.

Steph