In recent years, by increasing CPU and I/O devices demands, running multiple tasks simultaneously becomes a crucial issue. This paper presents a new task scheduling algorithm for multi-CPU and multi-Hard Disk Drive (HDD) in soft Real-Time (RT) systems, which reduces the number of missed tasks. The aim of this paper is to execute more parallel tasks by considering an efficient trade-off between energy consumption and total execution time. For study purposes, we analyzed the proposed scheduling algorithm, named HCS (Hard disk drive and CPU Scheduling) in terms of the task set utilization, the total execution time, the average waiting time and the number of missed tasks from their deadlines. The results show that HCS algorithm improves the above mentioned criteria compared to the HCS_UE (Hard disk drive and CPU Scheduling _Unchanged Execution time) algorithm.

In recent years, with an increasing number of requests, energy, power and temperature have been important keys in embedded systems, which decrease the lifetime of both CPUs and hard disks. The energy consumption is an important issue in computer systems, particularly real-time embedded systems. The frequency and the Revolutions Per Minute are major factors in the reduction of energy consumption in both processors and hard disk drives. Therefore, the main goal of this paper is to present a scheduling mechanism for a real time periodic task that can save more energy. This mechanism is based on increasing, as much as possible, the execution time of the CPU and/or the Read/Write time of the hard disk without passing the task deadline. This will be done by dynamically changing the CPU frequency and/or the RPM of hard disk. Our experimental results demonstrate that the proposed algorithm manages to lower energy consumption by an average of 25% and to reduce the number of missed tasks by 80%.