Smart Ethernet Network Interface Card

Although one of the immediate concerns of the NASD drive architecture is the network bandwidth and latency of the drive, it is quickly seen that performance limiting problems in the NASD network attachment are also present at the clients using NASD. Traditional software layering of wide and local area network protocols in many operating systems create a major bottleneck at the network input and output of workstations and personal computers. Performance measurements taken on contemporary workstations indicate network protocol processing can take as much as 45% of useful CPU cycles. Furthermore, network bandwidth is limited to tens of megabytes per second when network technologies such as FibreChannel and GigaBit Ethernet make raw network bandwidths of hundreds of megabytes per second possible.

One solution to this problem is perhaps a natural evolution of the current network interface hardware designs. The integration of a medium-performance processor onto the network interface not only makes possible the off-loading of protocol processing from the host CPU, but also provides a platform for flexible and programmable network interfaces. The intelligent NASD Ethernet card provides a 100 Mbps Ethernet interface, a StrongARM processor, up to 4 MB of RAM, and a high-speed PCI interface to the host system. A lightweight operating system running on the card makes it possible to dynamically switch different network protocols (or layers of protocols) into the network interface hardware. The reduced computational requirements and interrupt traffic at the host CPU free it for application software.

The NASD ethernet card design provides:

• A tool to investigate next generation network hardware designs. The requirement for more computational power at the network interface may be inevitable for NASDs running high-interoperability network protocols such as IP to be realised.
• A platform to investigate the performance gains and design tradeoffs of taking the current network hardware abstraction layer from descriptor rings of link level packets to Internet Protocol (IP), User Datagram Protocol (UDP) or even Remote Procedure Call (RPC) levels.
• Rapid prototyping of NASD client and drive networking and security designs in a limited computing environment similar to what might be expected in next generation harddisk drives.
• Experimenting with the integration of emerging standards like I2O with the NASD distributed and autonomous storage framework.