Download Disk Storage and Access Technologies: Homework 2 Solutions - Prof. Douglas Heisterkamp and more Assignments Computer Science in PDF only on Docsity! Homework 2 — Due September 3 • Exercise 7, 8, and 13, (pages 111,113) • Using the specifications from table 3.1 (on page 49) for the Western Digital Caviar AC22100, determine the estimated time to read a file of 6,451,200 bytes for the following two assump- tions: 1. Assume that the sectors are randomly dispersed over the disk surface (that is, can read only one sector at a time). 2. Assume that the sectors are store contiguously in tracks, but that the tracks are randomly dispersed over the disk surface (that is, can read one track at a time). Repeat the above calculations with the specifications from one of the current disk drives from exercise 7. 1 Message Board http://chat.okstate.edu/message board • Use your OSU student ID number as your login ID. • Your initial password is your default network password for OSU ( your default OSU email password). • You are encourage to change your password via the link on the login page. 2 Buffering • RAM disk — memory that simulates a disk • Disk cache — memory that contains pages of data from a disk. 5 Tapes • primarily used as archival storage. • sequential access — no direct access. • can be useful for sequential processing in that a tape can be dedicated to one process 6 CD-ROM Compact Disc, Read-Only Memory • Holds 650 MB of data • Uses: – Digital audio – Publishing medium – Archival storage 7 CLV vs. CAV • CDROMs use constant linear velocity (CLV) — the disc passes under the reading device at a constant rate→ con- stant data density, maximizes storage, disc spins at differ- ent rate for different sectors. • Disk drives use constant angular velocity (CAV) — the disk spins at a constant rate→ data density is less on outer tracks, easy to find the start of a sector. 10 Addressing • A sector is addressed by the minute,second, and sector of play→ 18:11:23 would be the twenty-third sector in the eleventh second of the eighteenth minute of play. • Each second of play hold 75 sectors, each of 2 kilobytes of data. • Audio data — two 16 bit samples at 44 kilohertz → 176,400 bytes per second. • The standard audio error correction would result in an av- erage of one incorrect byte for every two discs. The stan- dard data error correction results in an error rate of 1 byte in every 20,000 discs. 11 The future of CDROM? • 650 MB is small compared to most hard drives — may use 4-5 CDs to install a program • The need to run an application from CDROM is disap- pearing • Networks archives are competing with CDROM. • DVD • MP3 12
