scAN扫描算法 The disk arm starts at one end of the disk and moves toward the other end, servicing requests until it gets to the other end of the disk. where the head movement is reversed and servicing continues.磁头从磁盘的一端开始向另一端移动, 沿途响应访问请求,直到到达了磁盘的另一端,此时磁头反向 移动并继续响应服务请求。 Sometimes called the elevator algorithm.有时也称为电梯算 法。 Illustration shows total head movement of 208 cylinders. A 图所示,磁头移动的总距离是208柱面。 Applied Operating System Concepts 138 Silberschatz, Galvin, and Gagne @199913.8 Silberschatz, Galvin, and Gagne ©1999 Applied Operating System Concepts SCAN 扫描算法 • The disk arm starts at one end of the disk, and moves toward the other end, servicing requests until it gets to the other end of the disk, where the head movement is reversed and servicing continues. 磁头从磁盘的一端开始向另一端移动， 沿途响应访问请求，直到到达了磁盘的另一端，此时磁头反向 移动并继续响应服务请求。 • Sometimes called the elevator algorithm. 有时也称为电梯算 法。 • Illustration shows total head movement of 208 cylinders. 如 图所示，磁头移动的总距离是208柱面