Info 1410 Tutorial 4
INFO 1410 Tutorial 4 1 What are the advantages of using a glass substrate for a magnetic disk? Improvement in the uniformity of the magnetic film surface to increase disk reliability. A significant reduction in overall surface defects to help reduce read/write errors. Ability to support lower fly heights (described subsequently). Better stiffness to reduce disk dynamics. Greater ability to withstand shock and damage Explain the difference between a simple CAV system and a multiple zoned recording system For the constant angular velocity (CAV) system, the number of bits per track is constant. An increase in density is achieved with multiple zoned recording, in which the surface is divided into a number of zones, with zones farther from the center containing more bits than zones closer to the center. Define the terms track, cylinder and sector On a magnetic disk. data is organized on the platter in a concentric set of rings, called tracks. Data are transferred to and from the disk in sectors. For a disk with multiple platters, the set of all the tracks in the same relative position on the platter is referred to as a cylinder. What is the typical disk sector size? 512 bytes. Define the terms seek time, rotational delay, access time, and transfer time On a movable-head system, the time it takes to position the head at the track is known as seek time. Once the track is selected, the disk controller waits until the appropriate sector rotates to line up with the head. The time it takes for the beginning of the sector to reach the head is known as rotational delay. The sum of the seek time, if any, and the rotational delay equals the access time, which is the time it takes to get into position to read or write. Once the head is in position, the read or write operation is then performed as the sector moves under the head; this is the data transfer portion of the operation and the time for the transfer is the transfer time. What common characteristics are shared by all RAID