Chapter 3 Storage

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Learning Objectives

• Name several general characteristics of storage systems. • Describe the three most common types of hard drives

and what they are used for today. • Discuss the various types of optical discs available today

and how they differ from each other. • Identify some flash memory storage devices and media

and explain how they are used today. • List at least three other types of storage systems. • Summarize the storage alternatives for a typical personal

computer.

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Overview

• This chapter covers: – The characteristics common among all storage systems – The primary storage for most personal computers—the

hard drive – How optical discs work and the various types that are

available today – Flash memory storage systems – Network and cloud storage, smart cards, and the storage

systems used with large computer systems – Storage alternatives for a typical personal computer

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Storage System Characteristics

• A storage system consists of a storage medium and a storage device – The storage medium is the hardware where data is stored

• DVD disc, flash memory card, etc. – The storage device is the hardware into which the storage

medium is inserted • DVD drive, flash memory card reader, etc. • Can be internal, external, or remote • Storage devices are typically identified by letter

– Some storage media is removable; some is not

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Examples of Storage Device Identifiers

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Volatility and Random vs. Sequential Access

• Volatility – Storage media are nonvolatile and, therefore, is used for

data to be saved for later use • Random vs. sequential access

– Random access (direct access) allows data to be retrieved from any location on the storage medium

• Virtually all storage devices use random access – Sequential access means that retrieval of data can occur

only in the order in which it was physically stored on the storage medium; for example, a magnetic tape drive

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Files, Filenames, and Folders

• A file is anything stored on a storage medium, such as a program, document, digital image, or song

• A filename is a name given to a file by the user • A folder is a named place on a storage medium

into which files can be stored

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Logical vs. Physical Representation and Types of Storage Technologies Used

• Logical file representation – Individuals view a document stored as one complete unit

in a particular folder on a particular drive • Physical file representation

– Computers access a particular document stored on a storage medium using its physical location or locations

• Types of storage technology – Magnetic (conventional hard drives) – Optical (optical discs) – Electrons (flash memory media)

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Hard Drives

• A hard drive stores most programs and data for a personal computer – Can be internal or external – Available with built-in encryption that limits access to only

authorized users

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Magnetic Hard Drives

• A magnetic hard drive or hard disk drive (HDD) contains particles on the metal disks inside the drive that are magnetized to represent the data’s 0s and 1s

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Magnetic Hard Drives (cont’d)

• One or more metal hard disks are permanently sealed inside the drive along with an access mechanism and read/write heads

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Hard Disk Organization

• Tracks are concentric paths on the disk where data is recorded

• Sectors are small pieces of a track • Clusters consist of one or more sectors

• Smallest addressable area of a disk • Cylinders are a collection of tracks located in the same

location on a set of hard disk surfaces

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Examples of Tracks, Sectors, Clusters, and Cylinders

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Magnetic Hard Drive Technologies

• Traditional: Longitudinal magnetic recording aligns magnetic particles on a hard disk horizontally, parallel to the hard disk’s surface

• Newer: Perpendicular magnetic recording (PMR) places bits upright and closer together to increase capacity and reliability

• Newest: Shingled magnetic recording (SMR) squeezes more data onto disks by overlapping the data tracks on them like the shingles on a roof

• Emerging: Heat-assisted magnetic recording (HAMR) uses lasers to temporarily heat the surface of the hard disks when storing data in order to store more data

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How It Works

More Storage for Your Tablet • Tablets often have between

16 GB and 128 GB of storage • To extend storage, you can

transfer content to and from desktops or notebooks

• Easier to use a wireless hard drive and Wi-Fi – Download the

appropriate app The 2 TB Seagate Wireless Plus magnetic hard drive.

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Inside the Industry

Data Recovery Experts • Recover data from damaged storage devices • Used when devices are physically damaged or just stop

working • It is important to back up data to prevent data loss

Data recovery. The data on this destroyed computer (left) was recovered by data recovery experts in a clean room (right).

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Solid-State Drives (SSDs)

• A solid-state drive (SSD) uses flash memory technology to store data – Uses less power and has no

moving parts – Much faster than magnetic

hard drives, but more expensive

– The norm for netbooks, mobile devices, and other portable devices

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Solid-State Hybrid Drives (SSHDs)

• A solid-state hybrid drive (SSHD) or hybrid drive uses a combination of magnetic disks and flash memory chips – The data that is most

directly associated with performance is stored in the flash memory

– Nearly as fast as solid-state drives (SSDs)

– Slightly more expensive than magnetic hard disk drives (HDDs)

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Internal and External Hard Drives

• Internal hard drives are permanent storage devices located inside the system unit – Removed only if a problem develops

• External hard drives transport large amounts of data from one computer to another, for backup, and for additional storage – Full-sized external hard drives are often used for backup – Portable external hard drives: smaller and easier to

transport – Most connect with a USB connection, although some may

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Examples of External Hard Drives

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Hard Drive Speed and Disk Caching

• Disk access time is the total time that it takes for a hard drive to read or write data • Consists of seek time, rotational delay, and data

movement time • SSDs don’t require seek time or rotational delays

• Disk cache consists of memory used in conjunction with a magnetic hard drive to improve system performance – Typically consists of RAM-based disk cache located inside

the hard drive case – Can speed up performance and save battery life

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Hard Drive Partitioning

• Partitioning divides the physical capacity of a single drive logically into separate areas, called partitions – Each partition functions as an independent hard drive – Referred to as logical drives – Increases efficiency (smaller drives use smaller clusters)

• Partitions are used to create: – A recovery partition – A new logical drive

for data – A dual boot system

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Hard Drive File Systems and Interface Standards

• File system determines the partition size, cluster size, maximum drive size, and maximum file size – FAT, FAT32, and NTFS

• Interface standards determine how a drive connects to the computer

• Common standards – Serial ATA (SATA): most common internal hard drive

interface standard – Serial attached SCSI (SAS) – Fibre Channel – Internet SCSI (iSCSI)

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Quick Quiz (1)

1. Of the following three options, the storage media that would likely hold the most data is a(n) __________. a. HDD b. USB flash drive c. SSD

2. True or False: SSDs are subject to mechanical failures just like magnetic hard drives.

3. The circular rings on a magnetic disk on which data is stored are called __________.

Answers: 1) a; 2) False; 3) tracks Understanding Computers: Today and Tomorrow, 15th Edition 24

Optical Discs

• Optical discs are thin circular plastic discs – Are read from and written to using laser beams – Are commonly used for software delivery – Divided into sectors like magnetic discs but use a single

spiral track (groove) – Have a relatively large capacity and are durable – Used for backup purposes and for storing and transporting

music, photos, video, etc.

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Representing Data on an Optical Disc

• Pits and lands are used to represent 1s and 0s • The transition between a pit and a land represents a 1;

no transition represents a 0 • Read-only optical disc

– Surface of disc is molded or stamped to represent data • Recordable or rewritable disc

– The reflectivity of the disc is changed using a laser beam to represent the data

– Different types of optical discs use different types of laser beams

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How Recorded Optical Discs Work

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Optical Drives

• Optical discs are read by optical drives – The optical drive must support the type

of optical disc being used – Almost always backward-compatible – Recording data onto a optical disc is

called burning; requires burning software – Optical drives can be internal or external

• External drives typically connect via USB port

• External drives can be used with netbooks and other devices without an optical drive

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Optical Disc Shapes, Sizes, and Capacities

• Standard size is 120-mm (about 4.7 inches) – Mini discs are smaller (about 3 inches)

• Theoretically can be made into various shapes, but patent battle has resulted in custom shapes not being available

• Clear background is sometimes used to make a disc look custom shaped

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Advantage of Optical Discs

• Major advantage: Large capacity – CD discs are normally single layer and hold 700 MB – DVD discs hold 4.7 GB (single-layer) or 8.5 GB (dual-layer) – BD discs hold 25 GB (single-layer) or 50 GB (dual-layer) – BDXL standard uses even more layers to boost capacity up

to 128 GB – Newest BD discs are Ultra HD Blu-ray discs that hold up to

100 GB and are designed to deliver Ultra HD (4K) movies – Discs can also be double-sided

• Read on one side at a time; must be turned over to access the second side

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Summary of Optical Discs

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Read-Only Optical Discs: CD-ROM, DVD-ROM, and BD-ROM Discs

• CD-ROM, DVD-ROM, and BD-ROM discs can be written to, but not erased and reused – Pits are permanent – CD-ROM and DVD-ROM discs come prerecorded with

software, music, movies, etc. – BD-ROM discs come prerecorded with movies

• Ultra HD Blu-ray discs can be used for 4K movies – Additional proprietary read-only discs

• Gaming systems like Wii, Xbox, PlayStation, etc.

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Recordable Optical Discs: CD-R, DVD-R, DVD+R, and BD-R Discs

• CD-R, DVD-R, DVD+R, and BD-R discs can be written to, but cannot be erased and reused – Pits are created in the disc when the disc is recorded – Most discs have a recording layer containing organic light-

sensitive dye between disc’s plastic and reflective layers • BD-R discs use inorganic material instead

– DVD-R DL and DVD+R DL are dual-layer discs – BD-R DL discs are dual-layer discs; BD-R XL use 3 or 4 layers – Used for backing up files, sending large files to others, and

storing multimedia files

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Rewritable Optical Discs: CD-RW, DVD- RW, DVD+RW, and BD-RE Discs

• CD-RW, DVD-RW, DVD+RW, and BD-RE discs can be written to, erased, and overwritten just like magnetic hard disks – Uses phase change technology

• Heating and cooling process is used to change the reflectivity of the disc

– The capacities are the same as their read-only and recordable counterparts

– Appropriate for transferring large files from one computer to another or otherwise temporarily storing data (disc can be reused)

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Trend

Ultra HD (4K) • Is the next big step in high-definition

(HD) TVs and content • Four times the resolution of ordinary HD • Requires four times as much data as

regular HD video • Many Internet connections are not fast

enough to support the large amounts of data required for 4K quality

• Available for those individuals who have the speed and bandwidth to support it; also available on Ultra HD discs

An example of a 4K movie.

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Quick Quiz (2)

1. The capacity of the standard DVD disc is _____. a. 50 GB b. 650 MB c. 4.7 GB

2. True or False: A DVD-RW disc can be written to and rewritten to.

3. The tiny depressions, dark areas, or otherwise altered spots on an optical disc that are used to represent data are called __________.

Answers: 1) c; 2) True; 3) pits

Understanding Computers: Today and Tomorrow, 15th Edition 36

Flash Memory Storage Systems

• Flash memory is a chip-based storage medium that represents data using electrons – Used in a variety of storage systems

• Embedded flash memory refers to flash memory chips embedded into products – Smartphones, tablets, smart watches, and even sunglasses

and wristwatches – Usually the primary storage for mobile devices such as

tablets and smartphones

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Examples of Embedded Flash Memory

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This tablet contains 64 GB of embedded flash memory.

An embedded flash memory chip.

Flash Memory Cards and Readers

• A flash memory card is a small card containing one or more flash memory chips, a controller chip, and metal contacts to connect the card to the device or reader being used – Available in a variety of formats; these formats are not

interchangeable – Secure Digital (SD) is one of the most widely used types of flash

memory media – Most common type of storage media for digital cameras,

smartphones, and other portable devices • Many devices today have a built-in flash memory card reader;

an external reader via USB port is also used • Adapters allow the use of smaller flash memory cards in a

larger slot of the same type (microSD to SD, etc.)

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Examples of Flash Memory Cards, Readers, and Adapters

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Flash Memory Cards

• General-purpose flash memory card – Appropriate for most

applications • Specialized flash memory cards

– Professional flash memory cards

– Gaming flash memory cards – Encrypted flash memory cards

• Project Vault is a computer on a flash memory card

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