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In this paper, we evaluate the performance of a software iSCSI initiator over a software iWARP stack. Through measurements and simulations, we quantify the protocol processing costs of the iSER, Verbs, and iSCSI control layers in the fast path. We project the stack performance at a micro-benchmark level, by combining these costs with the protocol processing costs associated with a software iWARP stack developed at Intel. Our implementation is based on the Datamover Architecture. This allows us to compare the performance of the stack with an alternative iSCSI solution that we implemented on a TCP/IP transport stack. We present quantitative data comparing the two stacks by evaluating them with respect to different processing components like control processing, data placement, copy, and CRC. Our data shows that for software-only initiators, both stacks achieve equivalent performance for common iSCSI I/O sizes. Our results demonstrate that software iSCSI over iWARP on a general-purpose CPU does not carry a significant performance penalty over traditional software iSCSI. Therefore, future iSCSI-based storage over IP networks can benefit from the efficiency of RNIC-based storage targets while deploying a software iWARP stack for client storage initiators. |
