Chapter Two Input and Storage Devices Part II: Storage Devices

© Wiley, Inc. All Rights Reserved. Strata Objectives Covered 1.1 Identify basic IT vocabulary –USB, PS/2 1.3 Explain the characteristics and functions of internal and external storage devices 2

© Wiley, Inc. All Rights Reserved. Measurements of Storage Capacity SizeEqualsExample Byte8 bitsOne character of text Kilobyte (KB)1,024 bytesA 1,000-character plain text file or a tiny graphic Megabyte (MB)1,024 KB600 x 600 photo or one minute of a music clip Gigabyte (GB)1,024 MBFull length audio CD is 800 GB, a two-hour DVD movie is 4GB Terabyte (TB)1,024 GBLarge business database Petabyte (PB)1,024 TBAll the data for an entire government 3

© Wiley, Inc. All Rights Reserved. Maximum Storage Capacities Media FormatLargest as of 2011 Standard mechanical hard disk3 TB Solid state drive2 TB USB flash drive256 GB Compact flash card128 GB CD900 MB Blu-Ray50 GB Double-sided, double-density DVD 17 GB 4

© Wiley, Inc. All Rights Reserved. Hard Disk Drive Sealed stack of metal platters Read-write heads on a retractable arm Magnetizes bits of iron oxide particles on the platters in patterns of positive and negative polarity Platters rotate at a high speed 5

© Wiley, Inc. All Rights Reserved. Hard Disk Drive Can be internal or external Most computers have at least one internal hard disk drive External ones use USB or FireWire (IEEE 1394) connector Capacities ranging from a few hundred gigabytes (GB) to 3 terabytes (TB) 6

© Wiley, Inc. All Rights Reserved. Types of Hard Drive Connectors Parallel ATA (PATA) –Traditional interface –40-pin ribbon cable –Drives use a traditional Molex power connector 7

© Wiley, Inc. All Rights Reserved. Types of Hard Drive Connectors Serial ATA (SATA) –Newer interface, faster –SATA cable is thinner and less bulky –Seven-wire plug –Drives use a special power connector 8

© Wiley, Inc. All Rights Reserved. Types of Hard Drive Connectors Small Computer System Interface (SCSI) –Uses wider ribbon cable than PATA –Controller on board, not on drive –Less common in desktops –More common in servers and RAIDs –Drives use a traditional Molex power connector 9

© Wiley, Inc. All Rights Reserved. Factors that Govern Hard Disk Speed Rotational Speed –Measured in Revolutions Per Minute (RPM) Cache Size Interface Type –Serial ATA –Parallel ATA –SCSI –USB –FireWire 10

© Wiley, Inc. All Rights Reserved. RAID Redundant Array of Independent Disks –RAID 0 combines multiple devices to make one large drive, increasing performance –RAID 1 mirrors the content of one drive on another, increasing reliability –RAIDs 2 through 6 (5 is most common) increase both performance and reliability by striping data across three or more disks 11

© Wiley, Inc. All Rights Reserved. Low-Level Formatting Done at the factory when the disk is manufactured Defines the number of cylinders, heads, and sectors on the drive, which collectively determine its capacity 12

© Wiley, Inc. All Rights Reserved. Low-Level Formatting Because of addressing translation schemes, the physical number of heads, cylinders, and sectors may be different than what’s reported on the drive’s label When configuring a drive, use the values on its label 13

© Wiley, Inc. All Rights Reserved. Low-Level Formatting Cylinders: Number of unique positions of the read/write heads Same as number of tracks –A track is a concentric ring on an individual side of a platter –A cylinder is the collection of tracks at a certain read/write head position Heads: Number of platter sides Sectors: Number of segments that each track is divided into 14

© Wiley, Inc. All Rights Reserved. Partitioning a Disk Primary partition –All disks have one –Only the primary partition is directly bootable –A primary partition can have only one logical drive Extended partition –Optional, not all disks have one –Each extended partition can have one or multiple logical drives 15

© Wiley, Inc. All Rights Reserved. Partitioning a Disk Partitioning a disk creates a master boot record (MBR) –Contains information about each partition and logical drive –The OS looks to the MBR to determine what drive letters you have 16

© Wiley, Inc. All Rights Reserved. Partitioning a Disk Partitioning requires a disk management utility –Windows Setup –Disk Management (in Windows) –FDISK (in DOS and earlier Windows versions) –DISKPART (in Windows Recovery Console) 17

© Wiley, Inc. All Rights Reserved. High-Level Formatting Creates a filing system compatible with the OS NTFS is used for Windows-based systems Creates a Master File Table (MFT), a TOC for the logical drive Creates a volume boot record, storing info needed to boot from that drive Creates a root directory 18

© Wiley, Inc. All Rights Reserved. High-Level Formatting Sectors are grouped into clusters Also called allocation units Clusters are the smallest addressable unit in the file system Depending on the disk size and file system, a cluster can be from 1 to 128 sectors Each sector holds 512 bytes 19

© Wiley, Inc. All Rights Reserved. Creating Network Shares A network share is a shared network location, such as a drive or folder You can share a location on: –A file server –A user PC –Network attached storage (NAS) There are security and privacy risks whenever you share data 20

© Wiley, Inc. All Rights Reserved. Compact Discs and Drives Widely used for music and software distribution Optical media Store data in patterns of more and less reflective areas (lands and pits) 21

© Wiley, Inc. All Rights Reserved. Compact Discs and Drives CDs can store between 650 and 900 MB of data CDs can hold 74 to 99 minutes of audio 22

© Wiley, Inc. All Rights Reserved. Compact Discs and Drives CD speeds depend on their RPMs (revolutions per minute) –1x speed = 1.23 Mbps –56x speed = 68.8 Mbps 23

© Wiley, Inc. All Rights Reserved. Compact Discs and Drives Constant linear velocity –Data is read at a consistent rate –Disc spins at different speeds depending on where on the disc the data is located Constant angular velocity –Disc spins at a consistent speed –Data read rate depends on where on the disc the data is located 24

© Wiley, Inc. All Rights Reserved. Compact Discs and Drives CD and DVD interfaces –PATA –SATA –SCSI –USB (external) 25

© Wiley, Inc. All Rights Reserved. CD Writing Technologies Compact Disc Recordable –Can be written to once –Laser etches the die on the surface of the disc, making some areas less reflective to simulate pits Compact Disc Rewriteable –Can be written to, erased, and reused –Uses different laser write settings: High: Makes an area less reflective Low: Causes an area to go back to its original reflectivity 26

© Wiley, Inc. All Rights Reserved. DVD Disc and Drives Digital versatile disc, or digital video disc Single-sided, single-layer holds 4.7 GB of data Each disc can have up to two sides and up to two layers Two competing write technologies –DVD+R, DVD+RW –DVD-R, DVD-RW 27

© Wiley, Inc. All Rights Reserved. Blu-Ray Discs and Drives Similar to DVDs but can hold more data Use a blue laser rather than a standard red one Can hold 25GB per layer 28

© Wiley, Inc. All Rights Reserved. Flash RAM Storage Stores data in static (non-volatile) RAM –USB flash drives –Flash memory cards and readers –Solid-state hard drive –Mobile media devices (iPods, etc.) 29