Re: New List: rdma@cisco.com: to discuss RDMA

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

> However, I would support structuring the spec so that an RDMA
> transport mechanism could be used underneath (I guess that's
> motherhood).

Not necessarily.

You have to ask the implementors (particularly the hardware
implementors), what sort of optional RDMA proposal they'd be happy
with.  My answer is none.  It's mandatory or not at all.

The reason for using RDMA is to make the implementation of iSCSI
easier in hardware.  If there are implementations which do not support
the RDMA protocol, then your hardware implementation will have to
support both the `easy path' (using RDMA) and the `hard path' (no
RDMA).  If you have to implement the hard path anyway, there's no
point in implementing the easy path.

The argument that you could make the hard path infrequent and
implement it in software doesn't wash in this case.  It just takes one
implementation that doesn't do RDMA to slow your system to a crawl,
and the competitor who only implemented the non-RDMA path makes you
look like a fool.

Fundamentally, RDMA has to be either adopted or punted.  Of course,
I'm happy to have somebody prove this statement wrong.

Steph