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iSCSI/RDMA: Overview of DA and iSER

iSCSI/RDMA: Overview of DA and iSER. Mallikarjun Chadalapaka HP. Agenda. Motivation for iSCSI/RDMA iSER and DA? DA: Approach, why, principles iSER: big picture SCSI Read SCSI Write Next steps. Motivation for iSCSI/RDMA. Motivation

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iSCSI/RDMA: Overview of DA and iSER

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  1. iSCSI/RDMA:Overview of DA and iSER Mallikarjun Chadalapaka HP Mallikarjun Chadalapaka, HP

  2. Agenda • Motivation for iSCSI/RDMA • iSER and DA? • DA: Approach, why, principles • iSER: big picture • SCSI Read • SCSI Write • Next steps Mallikarjun Chadalapaka, HP

  3. Motivation for iSCSI/RDMA • Motivation • Take advantage of the RDMA protocol suite & RNIC hardware. • When RDMA technology advances, so does iSCSI. • Zero-copy, direct data placement can be achieved with generic protocols. • Opportunity for iSCSI protocol to offload some complexity • iWARP offers CRC-level reliability on TCP/IP. • iSCSI will be run on RNICs anyway, let’s make it optimal. • High-level goal: Run “most efficiently” on generic RNICs. Mallikarjun Chadalapaka, HP

  4. So what did we do? 2 discrete steps • Distill the data movement needs of iSCSI to propose an architecture for any “Datamover”. • DA (Datamover Architecture for iSCSI). • Based on the architecture, instantiate a Datamover protocol on RDMAP. • iSER (iSCSI Extensions for RDMA). Mallikarjun Chadalapaka, HP

  5. Why DA? • Principle: iSCSI is “assisted” by a Datamover protocol. • But by how much? • Are sessions offloaded? • How about login? • How about discovery? • DA draws a line through the iSCSI protocol functionality: • Data movement below, everything else above. • Everything “below the line” is assisted by a Datamover. • The “line” is defined by “Operational Primitives”. Mallikarjun Chadalapaka, HP

  6. Datamover Architecture Datamover {Layer, Protocol, Interface} iSCSI layer iSCSI layer Datamover Interface (DI) Datamover layer Datamover protocol Datamover layer Datamover-dependent TCP layer TCP layer Mallikarjun Chadalapaka, HP

  7. DA Design principles • Not a wire protocol spec. • A functional model of interactions within an iSCSI node. • Agnostic about hardware or software implementations. • Independent of iSCSI revision specifics, or of any Datamover protocol. • Motivated by RDMA but designed not just for iWARP. Mallikarjun Chadalapaka, HP

  8. iSER Big picture A TCP-based implementation is shown as an example. SCSI • Layered on RDMAP protocol. • iSCSI still requires direct TCP access for bootstrapping (login). • Transition to RDMA mode along with FFP. • Same iSCSI well-known port • Same discovery. iSCSI Datamover Interface 1 2 iSER iWARP Verbs RDMAP DDP Generic RDMA over TCP/IP iWARP protocol suite MPA TCP RNIC Mallikarjun Chadalapaka, HP

  9. iSCSI/iSER: Port to Port (FFP) Initiator Target Initiator Target SCSI target port SCSI initiator port SCSI target port SCSI initiator port I_T Nexus I_T Nexus SCSI SCSI I_T Nexus I_T Nexus iSCSI Session iSCSI Session iSCSI Connection iSCSI Connection iSCSI iSCSI Connection iSCSI Connection iSCSI Session iSCSI Session iSCSI Connection iSCSI Connection iSCSI iSCSI Connection iSCSI Connection TCP connection TCP connection DI iSCSI/iSER connection iSCSI/iSER connection iSCSI/iSER connection iSCSI/iSER connection iSER Verbs RDMAP Stream RDMAP Stream RDMAP Stream RDMAP RDMAP Stream DDP Stream DDP Stream DDP Stream DDP Stream DDP + MPA TCP connection Mallikarjun Chadalapaka, HP TCP connection

  10. SCSI Read Initiator Target Command encapsulated in a Send Type Message (Advertises initiator’s STag for the SCSI buffer) SCSI Command PDU Command Request SCSI Data-in PDU RDMA Write Message Read data back to the host Data transfer (all associated RDMA Writes complete) SCSI Response PDU SCSI Response PDU Encapsulated in a Send Type Message Command Complete Mallikarjun Chadalapaka, HP

  11. SCSI Write Initiator Target Command encapsulated in a Send Type Message (Advertises initiator’s STag for the SCSI buffer) SCSI Command PDU Command Request R2T PDU RDMA Read Request Message Write data from the host Data transfer (all associated RDMA Reads complete) SCSI Response PDU Response encapsulated in a Send Type Message Command Complete Mallikarjun Chadalapaka, HP

  12. Dependencies & Non-dependencies • DA is dependent only on iSCSI. • iSER is dependent on DA & iSCSI. • iSER is dependent only on the RDMAP protocol among the iWARP suite. • iSER & DA are not dependent on the RDMA Verbs. Mallikarjun Chadalapaka, HP

  13. Now & Next steps • I-Ds submitted in July 2003. • Now in their -02 revisions. http://www.ietf.org/internet-drafts/draft-chadalapaka-iwarp-da-02.txt http://www.ietf.org/internet-drafts/draft-ko-iwarp-iser-02.txt • Discussion on the IPS (and some on RDDP) reflector. • Proposal is to make DA and iSER drafts as the official IPS WG drafts,to eventually become standards-track RFCs. Mallikarjun Chadalapaka, HP

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