Mr. P. K. GuptaSandeep Gupta Roopak Agarwal

Road Map: Problem Statement Introduction Storage Systems And Storage Devices Brief Introduction To SAN and NAS DMA and RDMA How Does RDMA Works RDMA Application Future Work

Problem Statement What is the need and why such problems?

Problem Statement Network Bandwidth: 40%/yr CPU Power: x2 every 18 months Storage Capacity x2/yr Memory and I/O bandwidth?

A Server-to-Storage Bottleneck Source: Brocade

Brief Introduction SAN(Storage Network Area) and NAS(Network Attached Storage)

Storage Area Network (SAN) Storage accessed over a Fibre Channel switching fabric, using encapsulated SCSI.  Block level storage system  Fibre-Channel SAN  IP SAN Implementing SAN over well-known TCP/IP iSCSI: Cost-effective, SCSI and TCP/IP

NAS Network Attached Storage(NAS) Storage accessed over TCP/IP, using industry standard file sharing protocols like NFS, HTTP, Windows Networking  Provide File System Functionality  Take LAN bandwidth of Servers

Main Focus Today Technology Of DMA and RDMA and Future Work(iSER,RDMA over WAN....)

1/14/ Motivation for 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. High-level goal: Run “most efficiently” on generic RNICs.

Direct Memory Access (DMA) Direct Memory Access (DMA) is a capability provided that allows data to be sent directly from an attached device to the memory on the computer's motherboard.

Remote Direct Memory Access (RDMA) RDMA is a concept whereby two or more computers communicate via Direct memory Access directly from the main memory of one system to the main memory of another.

Working Of RDMA A simple concept.

DMARDMA

What Makes RDMA Advantageous ? There is no CPU cache or context switching overhead needed to perform the transfer. Transfers can continue in parallel with other system operations.

Some Objections to RDMA More complex API than TCP/stream interface – A new API is not required (but worthwhile for some applications) – Sockets Direct Protocol (SDP) Hardware vendors must all agree for approach to succeed in the market – –Extremely valid, but worth the cost Security concerns about opening memory on the network – Hardware enforces application buffer boundaries. – Makes it no worse than existing security problem with a 3rdparty inserting data into the TCP data stream.

RDMA Applications Clustered Database, Application Servers : They generate a large number of short messages, typically sent for synchronization and locking among nodes, so latency affects the degree to which they can scale. High performance Computing Storage Infrastructure

Future Work RDMA over WAN iSCSI extension for RDMA (iSER)

iSCSI Extension for RDMA (iSER) : Protocol that maps the iSCSI protocol, available from RDMA Only data transfer in iSCSI protocol is changed Reduces TCP/IP overhead

1/14/ iSER Big picture Layered on RDMAP protocol. iSCSI still requires direct TCP access for bootstrapping (login). – Transition to RDMA Same iSCSI well- known port SCSI iSCSI TCP Datamover Interface iWARP protocol suite RNIC iWARP Verbs Generic RDMA over TCP/IP 1 RDMAP DDP MPA iSER 2 A TCP-based implementation is shown as an example.

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