1

Storage Devices

Chapters 9 & 10

Ch 9 and 10

Ch 9 and 10 2

Magnetic Storage Device

• Uses magnetism to store data• Electricity flowing through a conductor creates

a magnetic field. • Moving a magnetic field near a conductor

creates electricity.• A digital signal is created by the rising and

falling voltage level (north / south pole)– Raising or Falling is a “1”– No change is “0”

Ch 9 and 10 3

Magnetic Storage DeviceHow it works• A fine layer of iron oxide coating

– Thin plastic TAPE– Thin plastic DISC– Glass, aluminum, ceramic DISC

• Conductor wound around a read/write head• Read / write head floats just .001 micron above spinning disc

platter – 5400 rpm (existing stock, slow-high storage)– 7200 rpm (good performance)– 10000 rpm (high performance-reduced storage)– 15000 rpm (highest performance-reduced storage)

Ch 9 and 10 4

Magnetic Storage Device

• Floppy Disc a soft magnetic disc used to store small to moderate amounts of information– 8” stored in paper jacket when not used (360 KB)– 5-1/4” package in hard paper or plastic jacket

(360 KB - 720 KB)– 3-1/2 durable plastic case (720 KB -2.88 MB)

• Floppy disc drive (floppy drive)– Used to read/write floppy disc– Only found on legacy machines / obsolete

Ch 9 and 10 5

Magnetic Storage Device

Ch 9 and 10 6

Magnetic Storage Device

Tape Drives• Earliest removable storage device• Hold tremendous amounts of data• Still used as backup (but declining fast)• Major disadvantage data must be read

sequentially• Being replaced by CD-RW, DVD, Flash

Ch 9 and 10 7

Magnetic Storage Device

Ch 9 and 10 8

Magnetic Storage Device

• Hard Drives essentially as stack of non- removable “hard” discs where the iron oxide coating is placed an a hard disc of glass, ceramic or aluminum.

• Unlike floppy drives hard disc drives have multiple R/W heads

Ch 9 and 10 9

Disc Geometry • Disc Geometry the surface of a floppy and hard

disc is divided into sectors, clusters and tracks. Hard Drives have stacks of discs and are also divided into cylinders

• Tracks are a set of concentric circles where data is stored

• Tracks are subdivided into sections called sectors– Smallest sector is 512 bytes

• Clusters are groups of sectors

Ch 9 and 10 10

Disc Geometry

Ch 9 and 10 11

Disc Geometry • When writing to a disk heads write to first available sector– Head 1 writes to first avail sector on top of disc 1– Head 2 writes to first avail sector on bottom of disc 1– Head 3 writes to first avail sector on top of disc 2…

• GUID Partition Table (GPT) and Master Boot Record (MRB) contain– MRB (when present)is located as a hidden protected area on the

first sector of the hard drive– Boot data– Disc partition Information

• # of sectors per cluster, clusters per tracks, # tracks, # of read write heads, and etc.

Ch 9 and 10 12

Disc Geometry

Ch 9 and 10 13

Disc Geometry Creating Disc Geometry• Low-Level Format: process that determines the

type of encoding to be done on the disk platter and the sequence in which the r/w/ head will access stored data

• Interleave factor describes the way the sectors are laid out on the disc surface

• Multiple Zone Recording (MRZ) also called zone bit recording sectors are all same size more on outer track than on inner tracks

Ch 9 and 10 14

Disc Geometry

Old style New style (MZR)

Ch 9 and 10 15

Disc Partition Systems

• When a disc is partitioned it is divided into separate storage area called logical drives

• not a separate physical drive but logical drives appear to users as separate drives (i.e. C: D: ect.)

• Partitions are set up for security, to allow smaller clusters, improved storage efficiency, faster data retrieval

• Active Partition is the partition from which the operating system will boot.

16

Disc Partition Systems• MBR Partition (master boot registry) all hard drives

must have at least one primary partition to contain operating system, boot, and data files– FAT 16 or FAT 32 (File Allocation Table) contain information

about where each file starts on the disc• FAT 16 - 4 GB max drive / 64 kB clusters• FAT 32 – 32 GB max drive / 16 kB clusters

– NTFS uses Master File Table to do what FAT does• NTFS – 2 TB max drive / 4 kB clusters

– Crash Dump status is a location where the operating system attempts to write information when a system failure occurs

Ch 9 and 10

Ch 9 and 10 17

Disc Partition SystemsGPT (Globally Unique identifier Partition Table) or GUID Partition Table• Doesn’t have limitations of MBR based partitions• Can handle large Hard drives up to 18 Exabyte

(EB) (Exabyte is approximately equal to one million terabytes)

• (ESP) EFI System Partition EFI = Extensible Firmware Interface– Requires GUID Partition Table

Ch 9 and 10 18

Disc Partition Systems• (MSR) Microsoft Reserved Partition• Proprietary Recovery Partition also known as OEM

partition – contains recovery tools, a copy of the operating system and any other files the manufacturer deems important

• UEFI Specification Partition Terminology developed as a guide for standardizing the way the partitions are arranged– Protective MBR established and is used to protect GPT

when legacy software is used– Protective MBR located first on hard drive followed by GPT

Ch 9 and 10 19

Disc Partition SystemsInitializing a Disk• The first file written to a new disk is the Disk

signature it identifies the disk type and properties so Microsoft operating system can utilize the disk

• GPT is automatically selected• If an additional Hard drive is installed the

initialize disk dialog box will appear– Follow prompts

Ch 9 and 10 20

Disc Partition SystemsPartitioning a Disk• DOS used Fdisk• DiskPart used since windows 2000

– Manages disk partitions and volumes– Used from command promt

• Disk Management: Preferred easy to use tool– Displays information about disk– Extend or shrink partition size– Add add’l drive and partitions– Format partitions– Change drive letters– Allocate amount of space each user can use– Run Chkdsk and disk defragmenter– Control Panel | Performance and Maintenance | Administrative Tools | Computer

Management

Ch 9 and 10 21

Disc Partition Systems

• Disk Quota: limit on amount of disk space allocated to each user

• Dynamic Disk: can keep increasing size of a volume by adding additional disk drives

• Disk Mirroring– Two-way mirror data is duplicated across two drives– Three-Way mirror data is written across two drive

and parity bits are written on third data can be written on new disk to automatically rebuild missing data

Ch 9 and 10 22

Disc Partition SystemsFormatting a Disk• Before it can be used a disk must be formatted (can also

format flash drives)• High-Level Format prepares disk to receive data (quick

format)– Identifies sectors– Marks bad sectors – Erases context of data table Data still there but not easily

recoverable without special software• Low-Level Format (full format)– Actually destroys all data – Checks and marks bad sectors

Ch 9 and 10 23

Disk File Maintenance

• Two common tools used for disk maintenance• Defragmenter and Chkdsk• Defragmenter– Fragmented disks are when files are stored in non

concurrent sectors /fragmented disks are slow– Disk become fragmented though normal

operation of modifying, deleting and saving files– Run as routine maintenance– Accessories | System Tools | Disk Defragmenter

Ch 9 and 10 24

Disk File Maintenance• Chkdsk is a utility that checks and repairs the

integrity of the file system on the hard drive. It checks for:– bad sectors– Lost / bad clusters– cross linked files– Directory structure errors– Explorer | properties | tools | check now

• Performance Measures: benchmark tests are performance tests used to compare different hardware

Ch 9 and 10 25

PATA and SATA Hard Disk Interface• ATA was a 16 bit used a 40 pin (later 80 pin) cable• PATA (parallel ATA) (now refered to as IDE drive)

integrated drive electronics or (EIDE Enhanced integrated drive electronics)– Motherboards usually have two IDE slots (IDE0 / IDE1)– Each slot (channel ) can support two physical drives– One drive must be designated master the other slave

because they share a cable– Master slave are set by jumpers

Ch 9 and 10 26

PATA and SATA Hard Disk Interface

• SATA (serial ATA) uses a thin, flat or round cable with only 7 conductors

• Uses less space in case• No master / slave• Only one SATA drive per motherboard slot• eSATA are hot swap devices

Ch 9 and 10 27

PATA and SATA Hard Disk Interface

PATA (IDE DRIVE) Cable SATA Cable