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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] 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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