TAILIEUCHUNG - Lecture Operating system concepts (Fifth edition): Module 13 - Avi Silberschatz, Peter Galvin

Module 13 - Secondary storage structure. In this chapter we describe the internal data structures and algorithms used by the operating system to implement this interface. We also discuss the lowest level of the file system the secondary storage structure. We first describe disk-head-scheduling algorithms. Next we discuss disk formatting and management of boot blocks, damaged blocks, and swap space. We end with coverage of disk reliability and stable-storage. | Lecture Operating system concepts Fifth edition Module 13 - Avi Silberschatz Peter Galvin Module 13 Secondary-Storage Disk Structure Disk Scheduling Disk Management Swap-Space Management Disk Reliability Stable-Storage Implementation Tertiary Storage Devices Operating System Issues Performance Issues Silberschatz and Galvin 1999 Disk Structure Disk drives are addressed as large 1-dimensional arrays of logical blocks where the logical block is the smallest unit of transfer. The 1-dimensional array of logical blocks is mapped into the sectors of the disk sequentially. Sector 0 is the first sector of the first track on the outermost cylinder. Mapping proceeds in order through that track then the rest of the tracks in that cylinder and then through the rest of the cylinders from outermost to innermost. Silberschatz and Galvin 1999 Disk Scheduling The operating system is responsible for using hardware efficiently for the disk drives this means having a fast access time and disk bandwidth. Access time has two major components Seek time is the time for the disk are to move the heads to the cylinder containing the desired sector. Rotational latency is the additional time waiting for the disk to rotate the desired sector to the disk head. Minimize seek time Seek time seek distance Disk bandwidth is the total number of bytes transferred divided by the total time between the first request for service and the completion of the last transfer. Silberschatz and Galvin 1999 Disk Scheduling Cont. Several algorithms exist to schedule the servicing of disk I O requests. We illustrate them with a request queue 0-199 . 98 183 37 122 14 124 65 67 Head pointer 53 Silberschatz and Galvin 1999 FCFS Illustration shows total head movement of 640 cylinders. Silberschatz and Galvin 1999 SSTF Selects the request with the minimum seek time from the current head position. SSTF scheduling is a form of SJF scheduling may cause starvation of some requests. Illustration .

• Hệ điều hành
• Operating system concepts
• Lecture Operating system concepts
• Operating system
• Hệ điều hành
• Computer system organization
• Secondary storage
• Operating system services
• Operating system structures
• Operating system design
• Operating system structure
• Operating System Debugging
• Operating System Generation
• Types of System Calls
• Computer system structures
• File system interface
• File system implementation
• Computer system architecture
• The Linux system