Re: Data in SCSI Response or SCSI Data

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

> Again I have to agree.  Not everyone writing this protocol is developing a
> hardware device.  Every time I (or any hardware vendor) sends one less IP
> packet down the wire is one less chance of it getting lost.

I do not think concessions should be made to software implementations
at the expense of hardware implementations.  Our experience is nobody
cares about a software network storage implementation if there are not
also hardware implementations.  The value proposition completely dries
up.  With available hardware implementations software implementations
become interesting.

I agree with Y.P. Cheng that implementing hardware for three ways to
find status IS a going to be a substantial irritation.  More
importantly, the outbound path of a hardware implementation (which
will include most targets) is very likely to chose to implement the
single easiest way for it, and use it in all cases.  In other words,
if data in one packet with RDMA information and status in a second
packet without is the natural way (seems like it), that's what you're
going to get coming back to the initiator.  Your software `fast path'
will never get exercised.

Even host `software' implementations are going to be able to support
various levels of hardware acceleration.  In the case of using a
hardware accelerated adapter, the host software will not see the data
packet, only the status.

Steph