Design and Implementation of IP-based iSCSI Offload Engine on an FPGA

Abstract

The IP-based storage systems often require bandwidth intensive access to storage devices, thus they exhibit high CPU utilization and low throughput when executed in a principally software implementation. This is especially evident for multi-Gbps networks where the impact of computational overhead is so pronounced that the current state of the art processors cannot take advantage of the capacity of the network. In this paper we propose new iSCSI Offload Engine architecture for high data rate storage networking. Based on our analysis of open source Open-iSCSI initiator, we offload the most computationally intensive and the most executed functions in a common case scenario, while other functions are implemented in a modified Open-iSCSI initiator on a general purpose processor. Our architecture overcomes the performance limitations imposed by a single processor which runs on 15x higher operating frequency than our accelerator. It exhibits very low CPU utilization of approximately 3% on the host CPU, which is 10-15x reduction compared with software implementation. The maximum transmission throughput is 7.81Gbps, while reception throughput is 7.34Gbps, which is 2 times speedup over software. The new architecture also shows comparable performance with Chelsio T110 ASIC-based HBA, and has more flexibility.