FAST '03 Abstract
Storage Over IP: When Does Hardware Support Help?
Prasenjit Sarkar, Sandeep Uttamchandani, and Kaladhar Voruganti, IBM Almaden Research Center
This paper explores the effect of the current generation of hardware support for IP storage area networks on application
performance. In this regard, this paper presents a comprehensive analysis of three competing approaches to
build an IP storage area network that differ in their level of hardware support: software, TOE (TCP Offload Engine)
and HBA (Host Bus Adapter). The software approach is based on the unmodified TCP/IP stacks that are part of a
standard operating system distribution. For the two hardware-based approaches (TOE, HBA), we experimented with
a range of adapters and chose a representative adapter for the current generation of each of the hardware approaches.
The micro-benchmark analysis reveals that while hardware support does reduce the CPU utilization for large block
sizes, the hardware support can itself be a performance bottleneck that hurts throughput and latency with small block
sizes. Furthermore, the macro-benchmark analysis demonstrates that while the current generation of the hardware
approaches may have the potential to provide performance improvements in CPU-intensive applications, overall the
analysis does not demonstrate any performance benefits in database, scientific and email benchmarks. The analysis in
this paper points out that a disparity in the processing power between the host and the adapter is the primary cause of
the performance bottleneck in the current generation of the hardware approaches. The paper aims to guide the designers
of the next generation of hardware-assisted adapters to better leverage the increasing processing power in the
host. In particular, future adapters should be capable of handling small operations at wire speed.
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