Questions and Answers
Which of the following are external memory devices? (Select all that apply)
Magnetic tape requires manual positioning to access data.
True
What is the main advantage of magnetic tape?
Low cost
How many tracks does magnetic tape store data in?
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A magnetic disk is coated with __________ material.
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What is the size of a universal sector on a magnetic disk?
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RAID level 1 duplicates all data.
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What is the purpose of parity information in RAID?
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What is the total number of disks in RAID level 2?
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What is one disadvantage of using Constant Angular Velocity (CAV)?
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Study Notes
External Memory Devices
- Types include Magnetic Tape, Magnetic Disk, RAID, Optical Memory, and SSD.
Magnetic Tape
- Utilizes magnetizable material on a flexible tape.
- Contains parallel tracks with nine tracks storing one byte each.
- Advantages: Low cost.
- Disadvantages: Requires sequential access and manual positioning for data retrieval.
Magnetic Disk
- Comprised of circular platters coated in magnetizable material.
- Employs a conducting coil (head) for read/write operations.
- Types include Floppy disk (single head) and others with dual heads for simultaneous operations.
- Data stored in concentric rings called tracks, divided into sectors of 512 bytes each.
- Formats involve specific data patterns at sector boundaries.
Data Formatting for Magnetic Disk
- Sector components:
- 17 Bytes for sector start
- 7 Bytes for sector ID
- 41 Bytes for gaps
- 512 Bytes of actual data
- 20 Bytes for sector end
Physical Characteristics of Magnetic Disk
- Head Movability: Fixed or movable.
- Mounting Method: Removable or non-removable.
- Number of Sides: Single-sided or double-sided.
- Platters: Single or multiple platters.
Head Mechanism in Magnetic Disk
- Consists of fixed distance to disk with physical contact.
- Air gap changes during operation for discs like Winchester disks.
Hard Disk Reading Mechanisms
- Constant Angular Velocity (CAV) and Multiple Zone Recording (MZR).
- MZR maintains constant data density, allowing higher storage capacity in inner sectors.
- CAV advantages: simplicity without complex circuitry and benefits with data balance.
RAID (Redundant Array of Independent Disks)
- Combines multiple physical disks viewed as one single logical drive.
- Distributes data among disks while using parity information for data integrity.
RAID Levels Overview
- RAID Level 0: Not a true RAID system; data distribution increases I/O transfer rates.
- RAID Level 1: Duplicates all data across two disks; enhances data recovery during disk failure.
- RAID Level 2: Includes additional disks for parity data, correcting single-bit errors with small strip sizes.
- RAID Level 3: Utilizes very small strips for high data transfer rates with parallel disk use.
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Description
This quiz covers various types of external memory devices, including magnetic tape and magnetic disks. It discusses their structure, advantages, and disadvantages, along with data formatting specifics. Ideal for students in information technology and computer engineering.
