Improving Energy Effeciency and Reliability of Disk Storage Systems

Numerous energy saving techniques have been developed to aggressively reduce energy dissipation in parallel disks. However, many existing energy conservation schemes have substantial adverse impacts on disk reliability. To remedy this deficiency, in this paper we address the problem of making tradeoffs between energy efficiency and reliability in parallel disk systems. Among several factors affecting disk reliability, the two most important factors - disk utilization and ages - are the focus of this study. We built a mathematical reliability model to quantify the impacts of disk age and utilization on failure probabilities of mirrored disk systems. In light of the reliability model, we proposed a novel concept of safe utilization zone, within which energy dissipation in disks can be reduced without degrading reliability. We developed two approaches to improving both reliability and energy efficiency of disk systems through disk mirroring and utilization control, enforcing disk drives to be operated in safe utilization zones. Our utilization-based control schemes seamlessly integrate reliability with energy saving techniques in the context of fault-tolerant systems. Experimental results show that our approaches can significantly improve reliable while achieving high-energy efficiency for disk systems under a wide range of workload situations

Operating-system support for distributed multimedia

Multimedia applications place new demands upon processors, networks and operating systems. While some network designers, through ATM for example, have considered revolutionary approaches to supporting multimedia, the same cannot be said for operating systems designers. Most work is evolutionary in nature, attempting to identify additional features that can be added to existing systems to support multimedia. Here we describe the Pegasus project's attempt to build an integrated hardware and operating system environment from\ud the ground up specifically targeted towards multimedia

Wide Area Network Access to CMS Data Using the Lustre Filesystem

In this paper, we explore the use of the Lustre cluster filesystem over the wide area network to access Compact Muon Solenoid (CMS) data stored on physical devices located hundreds of kilometres away. We describe the experimental testbed and report on the I/O performance of applications writing and reading data on the distributed Lustre filesystem established across the WAN. We compare the I/O performance of a CMS application to the performance obtained with IOzone, a standard benchmark tool. We then examine the I/O performance of the CMS application running multiple processes on a single server. And compare the Lustre results to results obtained on data stored on local filesystems. Our measurements reveal that the IOzone benchmark tool, accessing data sequentially, can saturate the Gbps network link that connects our Lustre client in Miami Florida to the Lustre storage located in Gainesville, Florida. We also find that the I/O rates of the CMS application is significantly less than what can be obtained with IOzone for sequential access to data