Post on 16-Feb-2017
Chapter 9Hard Drive Technologies
MELJUN CORTESMELJUN CORTES
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OverviewIn this chapter, you will learn to
Explain how hard drives workIdentify and explain ATA hard drive interfacesIdentify and explain SCSI hard drive interfacesDescribe how to protect data with RAIDExplain how to install drivesConfigure CMOS and install drivers
How Hard Drives Work
Historical/Conceptual
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The Hard Drive Hard drives are composed of individual disks
or platters
The platters are made up of aluminum and coated with a magnetic medium
Two tiny read/write heads service each platter
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The Hard Drive The closer the read/write heads are to the
platter, the more densely the data can be packed on to the drive
Hard drives use a tiny, heavily filtered aperture to equalize the air pressure between the exterior and interior of the hard drive
Platters spin between 3500 and 10,000 rounds per minute (RPM)
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Data Encoding Hard drives store data in tiny magnetic fields called
fluxes
The flux switches back and forth through a process called flux reversal
Hard drives read these flux reversals at a very high speed when accessing or writing dataFluxes in one direction are read as 0 and the other direction
as 1
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Data Encoding Encoding methods used by hard drives are
Run length limited (RLL) Data is stored using “runs” that are unique patterns of
ones and zeroesCan have runs of about seven fluxes
Partial Response Maximum Likelihood (PRML) Uses a powerful, intelligent circuitry to analyze each
flux reversalCan have runs of about 16 to 20 fluxesSignificantly increased capacity (up to 1 TB)
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Arm Movement in the Hard DriveThe stepper motor technology and the
voice coil technology are used for moving the actuator armMoves the arms in fixed increments or stepsOnly seen in floppies today
The voice coil technology uses a permanent magnet surrounding the coil on the actuator arm to move the armAutomatically parks drive over non-data area
when power removed
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Geometry Geometry is used to determine the location
of the data on the hard driveCHS (cylinders, heads, sectors)
Used to be critical to know geometryHad to enter into CMOS manually
Today, geometry stored on hard driveBIOS can query hard drive for geometry data
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HeadsHeads
Number of read/write heads used by the drive to store data
Two heads per platter (top and bottom)
Most hard drives have an extra head or two for their own usage, so the number may not be even
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CylindersCylinders
Group of tracks of the same diameter going completely through the drive
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Sectors per TrackSectors per track
Number of slices in the hard drive512 bytes per sector
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Obsolete Geometry Might see in older systems
Write precompensation cylinder The specific cylinder from where the drive would
start writing data farther apart Internal sectors physically smallerExternal sectors physically largerThis identified cylinder where spacing changed
Landing zone Unused cylinder as “parking place” for heads
Referred to as Lzone, LZ, ParkNeeded for older drives using stepper motors
ATA—The King
IT Technician
CompTIA A+Essentials
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Hard Drive Interfaces ATA interfaces dominate today’s market
Many changes throughout yearsParallel ATA (PATA) historically prominentSerial ATA (SATA) since 2003
Small Computer System Interface (SCSI)Pronounced “Scuzzy”Used in many high-end systems
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ATA Overview
Cable Keywords Speed Max sizeATA-1 40-pin PIO and
DMA3.3 MBps to 8.3 MBps 504 MB
ATA-2 40-pin EIDEATAPI
11.1 MBps to 16.6 MBps 8.4 GB
ATA-3 40-pin SMART 11.1 MBps to 16.6 MBps 8.4 GBATA-4 40-pin Ultra 16.7 MBps to 33.3 MBps 8.4 GBINT13 BIOS
Upgrade137 GB
ATA-5 40-pin80-wires
ATA/33 ATA/66
44.4 MBps to 6.6 MBps 137 GB
ATA-6 40-pin80-wires
Big Drive 100 MBps 144 PB
ATA-7 40-pin80-wires 7-pin
ATA/133
SATA
133 MBps to 300 MBps 144 PB
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ATA-1Programmable I/O (PIO)—traditional data
transfer3.3 MBps to 8.3 MBps
DMA—direct memory access2.1 MBps to 8.3 MBps
Allowed two drives (one master, one slave)
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ATA-2Commonly called EIDE (though a
misnomer)
Added second controller to allow for four drives instead of only two
Increased size to 8.2 GB
Added ATAPICould now use CD drives
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ATA-3Self-Monitoring Analysis and Reporting
TechnologyS.M.A.R.T.
No real change in other stats
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ATA-4Introduced Ultra DMA Modes
Ultra DMA Mode 0: 16.7 MBpsUltra DMA Mode 1: 25 MBpsUltra DMA Mode 2: 33 MBps
Ultra DMA Mode 2 also called ATA/33
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INT13 ExtensionsATA-1 standard actually written for hard
drives up to 137 GBBIOS limited it to 504 MB due to cylinder,
head, and sector maximumsATA-2 implemented LBA to fool the BIOS,
allowing drives to be as big as 8.4 GB
INT13 Extensions extended BIOS commandsAllowed drives as large as 137 GB
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ATA-5Introduced newer Ultra DMA Modes
Ultra DMA Mode 3: 44.4 MBpsUltra DMA Mode 4: 66.6 MBps
Ultra DMA Mode 4 also called ATA/66
Used 40-pin cable, but had 80 wiresBlue connector—to controllerGray connector—slave driveBlack connector—master drive
ATA/66 cable
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ATA-6“Big Drives” introduced
Replaced INT13 & 24-bit LBA to 48-bit LBA
Increased maximum size to 144 PB144,000,000 GB
Introduced Ultra DMA 5Ultra DMA Mode 5: 100 MBps ATA/100Used same 40-pin, 80-wire cables as ATA-5
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ATA-7Introduced Ultra DMA 6
Ultra DMA Mode 6: 133 MBps ATA/133Used same 40-pin, 80-wire cables as ATA-5Didn’t really take off due to SATA’s popularity
Introduced Serial ATA (SATA)Increased throughput to 150 MBps to 300
MBps
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IT TechnicianCompTIA A+Technician
ATA-7
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Serial ATASerial ATA (SATA) creates a point-to-point connection
between the device and the controllerHot-swappable
Can have as many as eight SATA devices
Thinner cables resulting in better airflow and cable control in the PC
Maximum cable length of 39.4 inches compared to 18 inches for PATA cables
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Serial ATAMore on SATA
PATA device my be connected to SATA using a SATA bridge
Can have as many as eight SATA devicesAdd more SATA functionality via a PCI card
eSATAExternal SATA
Extends SATA bus to external devices
eSATA Port
SCSISmall Computer System
Interface
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SCSIPronounced “Scuzzy”
Been around since ’70s
Devices can be internal or external
Historically the choice for RAIDFaster than PATACould have more than four drives
SATA replacing SCSI in many applications
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SCSI Chains A SCSI chain is a series of SCSI devices
working together through a host adapter
The host adapter is a device that attaches the SCSI chain to the PC
All SCSI devices are divided into internal and external groups
The maximum number of devices, including the host adapter, is 16
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Internal Devices Internal SCSI devices are installed inside
the PC and connect to the host adapter through the internal connector
Internal devices use a 68-pin ribbon cable
Cables can be connected to multiple devices
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External Devices External SCSI devices are connected to host adapter to
external connection of host adapter
External devices have two connections in the back, to allow for daisy-chaining
A standard SCSI chain can connect 15 devices, including the host adapter
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SCSI IDs Each SCSI device
must have a unique SCSI ID
The values of ID numbers range from 0 to 15
No two devices connected to a single host adapter can share the same ID number
No order for the use of SCSI IDs, and any SCSI device can have any SCSI ID
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SCSI IDs The SCSI ID for a particular device can be set
by configuring jumpers, switches, or even dials
Use your hexadecimal knowledge to set the device IDDevice 1 = 0 0 0 1 Off, Off, Off, OnDevice 7 = 0 1 1 1 Off, On, On, OnDevice 15 = 1 1 1 1 On, On, On, On
Host adapters often set to 7 or 15 but can be changed
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Termination Terminators are used to prevent a signal reflection that
can corrupt the signal
Pull-down resistors are usually used as terminators
Only the ends of the SCSI chains need to be terminated
Most manufacturers build SCSI devices that self-terminate
Protecting Data with RAID
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Protecting DataThe most important part of a PC is the data
it holdsCompanies have gone out of business
because of losing data on hard drives
Hard drives will eventually develop faults
Fault tolerance allows systems to operate even when a component failsRedundant Array of Inexpensive Disks (RAID)
is one such technology
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RAID Level 0Disk striping
Writes data across multiple drives at onceRequires at least two hard drivesProvides increased read and writes
Not fault tolerantIf any drive fails,
the data is lost
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RAID Level 1Disk mirroring/duplexing is the process of writing the
same data to two drives at the same timeRequires two drivesProduces an exact mirror of the primary driveMirroring uses the same controllerDuplexing uses separate controllers
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RAID Levels 2 to 4RAID 2
Disk striping with multiple parity drivesNot used
RAID 3 and 4Disk striping with dedicated parityDedicated data drives and dedicated parity
drivesQuickly replaced by RAID 5
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RAID Level 5Disk striping with distributed parity
Distributes data and parity evenly across the drives
Requires at least three drivesMost common RAID implementation
Software-based RAID 5
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RAID 5 (Stripe with Parity)Decimal 22 21 20
4 2 10 0 0 01 0 0 12 0 1 03 0 1 14 1 0 0
Decimal 21 20 OddParity
2 10 0 0 11 0 1 02 1 0 03 1 1 1
0
0
1
1
Data
0
1
0
1
Data
1
0
0
1
Parity
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RAID Level 6Super disk striping with distributed parity
RAID 5 with asynchronous and cached data capability
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Implementing RAIDSCSI has been the primary choice in the
pastFaster than PATAPATA allowed only four drives
SATA today viewed as comparable choiceSpeeds comparable to SCSIDedicated SATA controllers can support up to
15 drives
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Hardware vs. SoftwareHardware RAID
Dedicated controllerOperating system views
it as single volume
Software RAIDOperating system
recognizes all individual disks
Combines them together as single volume
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Personal RAIDATA RAID controller chips have gone down
in price
Some motherboards are now shipping with RAID built-in
The future is RAIDRAID has been around for 20 years but is
now less expensive and moving into desktop systems
Connecting Drives
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Connecting Your DriveChoosing your drive
PATA, SATA, or SCSICheck BIOS and motherboard for support
Jumpers and cabling on PATAMasterSlaveCable select
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Jumpers and Cabling
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Connecting SCSI DrivesFirst need compatible controller
Different types of SCSI
Connect data cableReversing this cable can damage drive, data, or
both
Connect powerPin 1 goes to Pin 1
Configure SCSI IDs on drives and controller
BIOS Support: Configuring CMOS and Installing Drivers
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Configuring CMOSEnable Controller
Turn on Auto detection
PATA - IDE Channels 1 and 2
SATA - IDE Channels 3 to 6
(note no slaves)
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Boot OrderIdentifies where computer will try to load
an operating system
Multiple devices configured
First one with an OS will boot
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Device DriversATAPI devices show up in CMOS, but true
BIOS support comes from a driver at boot-up
Serial ATA requires loading drivers for an external SATA controller and configuring the controller Flash ROM settings for the specific drive
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