SME Web Energy Efficient Platform (SWEEP): A new architecture for a hybrid web server

Web servers in Small and Medium Enterprises (SMEs) consume a significant amount of energy. Analysis of logs from an SME server has shown that the incoming request rate is on average low at less than 100 requests per minute with daily and weekly trends. We consider how a new hybrid SME web server architecture based on two co-located, mirrored platforms (a high-performance and high-power Master and a low-performance and low-power Assistant) can be architected to appear as a single system image to clients, significantly reduce energy consumption, and maintain an acceptable response time. A key contribution of our work is a new seamless method for switching between the two platforms in response to predicted request rates. Our new “macSwitch” method uses Gratuitous ARP and a handshake protocol between the Master and Assistant platforms – a separate load balancer is not needed, and requests are not lost during switching intervals. A prototype based on a Dell Pentium 4 – based PC and a Sheeva ARM – based plug computer was developed and evaluated using the Apache Benchmark (ab) and a workload based on the actual request log data from the main KETI web server. Using Exponentially Weighted Moving Average (EWMA) for predicting future request rates to trigger switching between the Assistant and Master, our experimental results show that for up to 50 requests per minute the hybrid system can sleep for 50% of the time with no increase in response time (compared to the response time of the Master only).