Disk-aware Request Distribution-based Web Server Disk Power Management

Abstract — This report presents studies, implementation, and simulation we conducted for the course project of COS518, Fall 2003. The course project was concerned with reducing power consumption by cluster-based web servers. We focused on server hard disks, a major source of server power consumption. We started with the modification of Logsim, a simulator for cluster-based web servers. The new simulator, NLogsim behaves exactly like a cluster-based web server handling requests when they arrive. Based on NLogsim, we exposed the relationship between file-cache size, workload, and disk idle periods. We explored the possi-bility of turning disks off dynamically according to the clus-ter’s performance and distributing requests in a disk-aware fashion. Based on our disk-aware request distribution, we show that up to more than 70 % of time, disks can be turned off with a reasonable rate of disk switchings and without significantly affect the cluster’s performance. This may lead to a more than 2.5X disk power reduction. We also show that disk power management is complementary to CPU and whole server power management, and in most times more flexible and effective than server power management. I