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    RE: VI (Was: Avoiding deadlock in iSCSI)



    
    
    I think several of us have stated that we would love and RDMA that is good
    for iSCSI, NFS,
    etc.. I doubt that a full-VI is the right answer but an RDMA mechanism
    satisfying
    both would be fine.  But this will take time - and although related -
    should not stop us from moving ahead.
    
    Julo
    
    Stephen Byan <Stephen.Byan@quantum.com> on 18/09/2000 17:07:04
    
    Please respond to Stephen Byan <Stephen.Byan@quantum.com>
    
    To:   IPS Reflector <ips@ece.cmu.edu>
    cc:    (bcc: Julian Satran/Haifa/IBM)
    Subject:  RE: VI (Was: Avoiding deadlock in iSCSI)
    
    
    
    
    Douglas Otis [mailto:dotis@sanlight.net] wrote:
    
    > Charles,
    >
    > Depending on the capabilities of the Net-SCSI adapter, such
    > direct copies
    > would be possible without resorting to VI.  Not using VI but
    > allowing direct
    > placement also provides lower overhead and a safer system as
    > pointers going
    > astray due to a muddled target or bit rot is not a concern.
    > SAM requires
    > buffers to be in place prior to issuing the request.  These
    > buffers are at
    > the client which is where VI becomes useful.  Unless both ends of this
    > communication becomes VI, you have not provided a meaningful solution.
    
    It may be better/more efficient/easier/whatever to implement iSCSI directly
    over TCP rather than over VI over TCP. My point was that in return for the
    pain, we can leverage the utility of the RDMA hardware assists, since the
    assists would be encapsulated in the VI layer, rather than intimately part
    of the iSCSI protocol. Consequently the RDMA hardware could be reused to
    accelerate other new protocols, as well as cluster message passing.
    
    I think an enlarged market for the hardware is important in order to ensure
    the success of iSCSI.  iSCSI depends on getting RDMA hardware acceleration
    NICs into the servers. Consider two product scenarios:
    
    1) a NIC with RDMA hardware acceleration for iSCSI.
    2) a NIC with RDMA hardware acceleration for iSCSI, DAFS, MPI, Oracle
    Parallel Server, DB2 extended edition, and which is open to future
    applications.
    
    Which product do you think would be the easiest to sell to an end-user
    customer?
    
    > Adding VI modifies TCP.
    
    I don't believe draft-dicecco-vitcp-00.txt modifies TCP in any way.
    
    However, I do think the proposed TCP Message Boundary Option would be
    useful
    in order to optimize the implementation of RDMA in either iSCSI or in
    VI/TCP.
    
    Regards,
    -Steve
    
    Steve Byan
    <stephen.byan@quantum.com>
    Design Engineer
    MS 1-3/E23
    333 South Street
    Shrewsbury, MA 01545
    (508)770-3414
    fax: (508)770-2604
    
    
    
    


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