An Overview of Global Seek Optimizing Real-Time Database Algorithms

The aim of conventional disk scheduling algorithms is to optimize the disk throughput. To meet time constraints, some conventional real-time algorithms, such as Earliest Deadline First (EDF), can be used to schedule disk I/O requests. However, the relative position of requested data on the disks is ignore by such algorithms. Because of large seek time and rotation latency, their throughput is relatively low. Several hybrid real-time algorithms were proposed, to keep a good tradeoff between optimizing throughput and meeting time constraints. The SCAN-EDF combines the features of SCAN type of seek optimizing algorithm with an Earliest Deadline First (EDF) type of real-time scheduling algorithm. Deadline-Modification-SCAN (DM-SCAN) that suggests the use of maximum-scannable-groups compute the suitable request group for seek-optimizing with guaranteed real-time requirements for rescheduling. Global Seek-optimizing Real-time (GSR) disk scheduling algorithm improve the system performance. A new algorithm based on GSR that is called IGSR (Improved GSR). This proposed method improves throughput and decreases the number of missed deadline. Performance evaluation showed IGSR decreased the number of missed deadlines and increased disk throughput in compare with GSR. TGGSR achieves higher disk throughput as compare to EDF and GSR.