RE:Why FCP doesn't need RDMA? It has a better way.

[Robert Snively <rsnively@Brocade.COM>]

>  I object to mandating iSCSI use an RDMA option because:
>  
>  - (main reason) there isn't any standardized mechanism now, and I
>    don't want to hold up iSCSI while one crawls through the 
>  standards process.
>  
>  - I don't think RDMA is needed.  FCP doesn't use it, and it 
>  works great with
>  the
>    FC protocol chips that "accelerate" FCP.

Actually, RDMA is not needed in FCP because all protocol chips
implemented perform a real peer-to-peer DMA straight to the 
data areas specified by the user's interaction with the operating
systems allocation algorithms.  The combination of the FCP/SCSI
pointer structure, task tagging, and the FC relative offset perform the
function you would otherwise have to use RDMA to accomplish.

Bob Snively
Brocade Communications           Phone  408 487 8135
1745 Technology Drive
San Jose, CA 95110               Email   rsnively@brocade.com