Chapter 4: Storage Devices

Introduction to Computers

• The presentation is about Storage Devices, specifically exploring different types and their characteristics.

Chapter 4: Storage Devices

• This chapter focuses on storage devices.

Lesson 5: Types of Storage Devices

• The lesson covers various categories of storage devices.

Introduction

• Storage devices are hardware used to store, transfer, and retrieve data files.
• There are two types of storage: primary and secondary.
• Primary memory is volatile and holds small amounts of data (e.g., RAM).
• Secondary memory is non-volatile and stores significant amounts of data (e.g., hard disks, CDs).

Categorizing Storage Devices

• Storage devices store data, even when the computer is off.
• A storage medium is the physical material holding the data.
• A storage device manipulates the storage medium.
• Primary storage technologies are magnetic and optical.
• A third category is solid-state storage.

Describing Storage Devices

• Storage involves writing and reading data.
• Storage media are materials that store data.
• Storage devices manage the media.
• Magnetic storage utilizes magnets.
• Optical storage uses lasers.
• Solid-state storage uses physical switches.

Magnetic Storage Devices

• Key magnetic storage types include hard disks and magnetic tape.

Optical Storage Devices

• Key optical storage types include CD-ROM, DVD-ROM, CD-R, and CD-RW.

Magnetic Storage Devices - How it Works

• Magnetic media are coated with iron oxide particles.
• Read/write heads are magnets that, by writing charges on the media, store data, recording positive charges as 1s and negative as 0s.
• Drives convert these charges into binary representation.

Magnetic Storage Devices - Data Retrieval

• Charged media particles are read by a read head which translates the charge to binary data.
• Iron particles are oriented in a way by the flow of current, allowing organized data storage.

How Data is Stored on a disk

• Data is stored on a magnetic disk by orienting tiny iron particles to represent binary bits (1 or 0).
• Read/write heads, containing electromagnets, create these magnetic charges.

How Data is Organized on a Magnetic Disk - Formatting

• Disks need formatting before use.
• This process defines the disk's surface layout for data storage.
• Formats create tracks and sectors on the disk, ensuring data organization.
• Sectors can hold up to 512 bytes, and each sector has a unique number for easy access.

Magnetic Storage Devices - Hard Disks

• Hard disks are primary storage devices using multiple stacked platters within a spindle.
• Each platter has two surfaces, each with a read/write head.

Illustrated Hard Disk

• Hard disks have platters with magnetic coatings, read/write heads, access arms, and spindles for rotation.

Magnetic Storage Devices - Hard Disks (Continued)

• Hard disks rotate at speeds of 3,600, 7,200, or 10,000 revolutions per minute.
• Hard disks are used to store extensive amounts of data.
• Access time for hard disks is around 9.5 milliseconds typically.

Magnetic Storage Devices - Tape Drives

• Tape drives offer large capacities and low cost but have slow sequential access.
• Tape drives are best suited for backups due to slow data access.

Optical Storage Devices - How Optical Storage Works

• Data is read in optical storage by reflected light from the disk's surface.
• Storage is accomplished using tiny pits and flat lands on the surface.
• Pits prevent light reflection, representing a '0' (off).
• Lands reflect light, representing a '1' (on).

Optical Storage Devices - How Optical Storage Works (Continued)

• A laser light beam reads data by reflecting off lands or scattering off pits.
• Rotation of the disk and precise positioning of the laser are crucial for efficient data handling.

Optical Storage Devices - CD-ROM

• CD-ROM is a common optical storage method in PCs.
• Standard CD-ROMs store up to 650 MB of data.
• Data on a CD-ROM can't be modified after creation.

Optical Storage Devices - CD-ROM Speeds and Uses

• Early CD-ROM drives operated at 150 KBps data transfer rates (compared to the 5 to 15 MBps of hard disks).
• Modern drives can achieve data transfer speeds up to 7800 KBps, contributing to more efficient work.
• CDs are predominantly used for software distribution, audio, video, and program instructions.

Optical Storage Devices - DVD-ROM

• DVD-ROM is a CD-ROM upgrade, now more used in PCs.
• Standard DVDs can store up to 9.4 GB of data.
• Dual-layer DVDs can store up to 17 GB, utilizing both sides and compression techniques.

Optical Storage Devices - Other Optical Storage Devices

• CD-Recordable (CD-R) allows recording your own CDs.
• CD-Rewritable (CD-RW) enables data overwriting on the same disc.
• DVD-Recordable (DVD-R) systems allow data recording to DVDs, which cannot be changed afterward.
• DVD-RAM enables reusable DVD media.

Solid-State Storage Devices

• Solid-state storage (SSD) employs integrated circuits for data storage.
• Unlike HDDs (hard drive), SSDs have no moving parts, leading to better durability and speed.

Solid-State Storage Devices (Continued)

• SSDs deliver faster data access than HDDs, improving overall system performance.
• Their durability makes them resistant to physical shock.
• Lower power consumption is beneficial for portable devices.

Flash Memory

• Flash memory is a lightweight, fast storage device.
• It's characterized by high storage capacity, small size and no need for electrical power to retain its contents.

Measuring and Improving Drive Performance

• Performance analysis involves average access time and data transfer rates.
• Average access time (or seek time) estimates time needed to locate data.
• The transfer rate assesses how fast data can be read or written.

Drive Performance (Continued)

• Average access time is measured in milliseconds.
• RPM (revolutions per minute) and time to access a track affect average access time for hard disk drives and CDs.
• Hard drives have an average access time of 6–12 ms; CDs are around 80–800 ms.
• Data transfer rate is measured in Bits Per Second (bps) or Megabytes per Second (MBps).
• Hard drives typically range from 15 to 160 MBps, while CDs are slower, ranging from 300 to 900 KBps.

Optimizing Disk Performance

• Disk optimization is often handled by routine operating system tools.
• Monthly optimization is recommended to ensure consistent efficiency.

Optimizing Performance (Continued)

• Cleaning up temporary files (e.g., .tmp files) and uninstalling unused programs can improve performance.
• Regular disk scanning fixes bad sectors, ensuring uninterrupted operation.
• Disk defragmentation reorganizes fragmented files for enhanced performance.

Optimizing Performance - File Compression

• File compression reduces file size and increases storage capacity.
• WinZip and WinRAR are examples of file compression software.

This quiz explores different types of storage devices as covered in Chapter 4. Learn about primary and secondary storage, their characteristics, and the technologies involved. Test your knowledge on how various storage mediums operate and their roles in data management.