Introduction to Computers PDF

Introduction to Computers Dr.Eng. Mahmoud Abu_Alfutuh Chapter 4 Storage Devices lesson 5 Types of Storage Devices This lesson includes the following sections: Introduction Magnetic Storage Devices Optical Storage Devices Solid-State Storage Devices...

Introduction to Computers Dr.Eng. Mahmoud Abu_Alfutuh Chapter 4 Storage Devices lesson 5 Types of Storage Devices This lesson includes the following sections: Introduction Magnetic Storage Devices Optical Storage Devices Solid-State Storage Devices Measuring and Improving Drive Performance  Introduction Storage device is hardware that is used for storing, porting, or extracting data files. Types of storing devices: Primary Memory: It is volatile storage. Data size is small. RAM is an examples of primary storage. Secondary Memory: It is non-volatile. Data size is large. Hard Disks and CDs are examples of secondary storage.  Categorizing Storage Devices Storage devices hold data, even when the computer is turned off. The physical material that holds data is called a storage medium. The hardware that writes data to or reads data from a storage medium is called a storage device. The two primary storage technologies are magnetic and optical. A third category of storage is solid-state storage.  Describing Storage Devices Storage involves two processes: Writing data Reading data Storage terms Media is the material storing data Storage devices manage the media Magnetic devices use a magnet Optical devices use lasers Solid-state devices have physical switches The primary types of magnetic storage are: Hard disks Magnetic tape The primary types of optical storage are: Compact Disk Read-Only Memory (CD- ROM) Digital Video Disk Read-Only Memory (DVD-ROM) CD-Recordable (CD-R) CD-Rewritable (CD-RW) Magnetic Storage Devices How Magnetic Storage Works Formatting Hard Disks Tape Drives Magnetic Storage Devices Most common form of storage Hard Disk and tape drives All magnetic drives work the same  Magnetic Storage Devices Data storage and retrieval – Media is covered with iron oxide – Read/write head is a magnet – Magnet writes charges on the media Positive charge is a 1 Negative charge is a 0 – Magnet reads charges – Drive converts charges into binary  Data Retrieval 6A-13  How Data Is Stored on a Disk A magnetic disk's medium contains iron particles, which can be polarized—given a magnetic charge—in one of two directions. Each particle's direction represents a 1 (on) or 0 (off), representing each bit of data that the CPU can recognize. A disk drive uses read/write heads containing electromagnets to create magnetic charges on the medium.  Write head Medium Random particles Current flow (no data stored) (write operation) Organized particles (represent data)  As the medium rotates, the head writes the data.  How Data is Organized on a Magnetic Disk - Formatting Disks must be formatted before use. A process that maps the disk's surface and determines how data will be stored. Format draws tracks on the disk Tracks is divided into sectors A sector can store up to 512 bytes (0.5 KB). All the sectors are numbered, so that the computer can access each small area on the disk by using a unique number. Formatted Disk  Magnetic Storage Devices - Hard Disks Primary storage device in a computer. Hard disks use multiple platters, stacked on a spindle. Each platter has 2 sides Each platter has two read/write heads, one for each side.  Illustrated Hard Disk 6A-20  Magnetic Storage Devices - Hard Disks Hard disks spin at a speed of 3,600, 7,200, or 10,000 revolutions per minute (rpm). Hard disks store large amounts of data. The average access time for hard disks is about 9.5 milliseconds. Read/write heads  Magnetic Storage Devices -Tape Drives Tape Drives provide large capacities and low cost. Tape Drives use slow sequential access. Tape Drives offer very slow data access. Tape drives are used mainly for backups. Optical Storage Devices How Optical Storage Works CD-ROM CD-ROM Speeds and Uses DVD-ROM Other Optical Storage Devices  Optical Storage Devices Optical Storage is a high-capacity storage medium. Optical systems, including CD-ROM, DVD- ROM, and their variants. These devices fall into the category of optical storage because they read data by a beam of laser light.  How Optical Storage Works An optical drive uses reflected light to read data. To store data, the disk's metal surface is covered with tiny pits and flat lands, which cause light to be reflected differently. When an optical drive shines light into a pit, the light cannot be reflected back. This represents a bit value of 0 (off). A land reflects light back to its source, representing a bit value of 1 (on). 1 0  How Optical Storage Works Read using a laser o Lands, binary 1, reflect data. o Pits binary 0, scatter data.  Optical Storage Devices – CD-ROM In PCs, the most commonly used optical storage technology is called Compact Disk Read-Only Memory (CD-ROM). A standard CD-ROM disk can store up to 650 MB of data. Once data is written to a standard CD-ROM disk, the data cannot be altered or overwritten.  Optical Storage Devices – CD-ROM Speeds and Uses Early CD-ROM drives were called single speed and read data at a rate of 150 KBps. (Hard disks transfer data at rates of 5 – 15 MBps). CD-ROM drives now can transfer data at speeds of up to 7800 KBps. Data transfer speeds are getting faster. CD-ROM is typically used to store software programs. CDs can store audio and video data, as well as text and program instructions.  Optical Storage Devices - DVD-ROM A variation of CD-ROM is called Digital Video Disk Read-Only Memory (DVD-ROM) and is being used in place of CD-ROM in many newer PCs. Standard DVD disks store up to 9.4 GB of data. Dual-layer DVD disks can store up to 17 GB. DVD disks can store so much data because both sides of the disk are used, along with sophisticated data compression technologies.  Optical Storage Devices - Other Optical Storage Devices A CD-Recordable (CD-R) drive lets you record your own CDs, but data cannot be overwritten once it is recorded to the disk. A CD-Rewritable (CD-RW) drive lets you record a CD, then write new data over the already recorded data.  Optical Storage Devices - Other Optical Storage Devices DVD-Recordable (DVD-R). Like CD-R, a DVD-R system lets you record data. Once you record data onto a DVD-R disc, you cannot change it. DVD-RAM- Allow reusing of DVD media.  Solid-State Storage Devices Solid-state storage (SSS) devices represent a modern approach to data storage. They are a type of data storage technology that utilizes integrated circuits to store data. Unlike traditional storage devices, such as hard disk drives (HDDs), solid-state drives (SSDs) have no moving parts, which contributes to their durability and speed  Solid-State Storage Devices Advantages of Solid-State Storage: Speed: SSDs provide faster data access compared to HDDs, enhancing overall system performance. Durability: With no moving parts, solid-state devices are more resistant to physical shock. Energy Efficiency: They consume less power, which is beneficial for battery-operated devices.  Flash Memory Flash memory is a lightweight and fast storage unit for storing and retrieving data. It is characterized by the following: - Large storage capacity. - Small size. - Does not require electrical power to retain its contents.  Measuring and Improving Drive Performance When evaluating the performance of storage devices, two common measures must be considered: Average access time Data transfer rate.  Drive Performance Average access time Also known as seek time Time to find desired data Measured in milliseconds Depends on two factors – RPM: speed at which a disk spins – Time to access a track Hard drive between 6 and 12 ms CD between 80 and 800 ms  Drive Performance Data transfer rate How fast data can be read Measured in Bps or bps Hard drive ranges from 15 to 160 MBps CD-ROMs are the slowest storage devices. CD-ROMs range from 300 KBps to 900 KBps.  Data Transfer Rate 6B-40  Optimizing Disk Performance Disk optimization – Handled by operating system tool – Routine disk maintenance – Optimization should be run monthly  Optimizing Performance Clean up unnecessary files – Delete temp files: filename extension.tmp – Uninstall unused programs – Files should be cleaned weekly – Removing unneeded programs can improve your computer’s performance.  Optimizing Performance Scan a disk for errors – Bad spots on the media – Find and fix the error – Move data to a good spot – Mark the spot as bad – Disks should be scanned monthly – Several versions of Windows have built-in disk- scanning utilities  Optimizing Performance Defragment a disk – Files fragment when resaved – Fragmented files load slower – Defragment puts the fragments together – Disks should be defragged monthly – Windows features a built-in defragmentation utility, called Disk Defragmenter.  Optimizing Performance File compression – Shrinks the size of a file – Takes up less space on disk – Will increase disk capacity – WinZip and WinRAR Thank you Thank you