Re: iSCSI: Flow Control

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

Joshua Tseng wrote:
> Not doing RTT means each write command must be completed atomically
> before proceeding on to the next command.  There will be some very
> large data PDU's hogging the single connection.  How about task
> management functions which the initiator may want to deliver
> asynchronously?  With a large data PDU stuck in the connection,
> (and commands stuck in the pipeline) it may require a more
> catastrophic abort/reset of the entire TCP connection, which might
> not have been originally necessary.
> 
> Somehow, it seems to me that the SCSI folks put RTT in there for
> a purpose, and iSCSI would be losing something by eliminating it.
> I don't know exactly what this is, but I would think it includes
> AT LEAST some performance impact.

I understand the basis of RTT is in the SCSI legacy of targets
with very small buffers where limits might be in the order of
single digits.  With modern buffers and cheap memory I question
its need.

	-David