Re: Data in SCSI Response or SCSI Data

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

> Is there anything preventing your hypothetical hardware implementor
> to send always good status within the last block of data?

It depends upon the RDMA mechanism you are using.  I admit that I have
not studied them in detail, other than ST of course, which is
essentially an transport protocol based upon a particular RDMA
mechanism.  I will try to do so soon to determine if I'm all wet.

However, assuming that the RDMA mechanism operates on a per-datagram
basis, I can only imagine that you will not be able to append
`general delivery' data to the end of an RDMA datagram.  In this case,
you will need a separate datagram to ensure that status is delivered
through a separate path from the data.

So, while I think concatenating status and data in its general form is
not a good idea, a good-status fast path (like the success bit) is
definitely the right way to think about it.  Nonsuccess SCSI status is
so rare that any compromise you can make in the nonsuccess path to
make the success path go faster is worth it.

Steph