Presentation on Hard disk

Storage• What is storage?• Holds data, instructions, and information for future use

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Storage medium is physical material used for storage

Storage Capacity– Number of bytes (characters) a storage medium can hold

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Kilobyte (KB) 1 thousand

Megabyte (MB) 1 million

Gigabyte (GB) 1 billion

Terabyte (TB) 1 trillion

Petabyte (PB) 1 quadrillion

Exabyte (EB) 1 quintillion

Zettabyte (ZB) 1 sextillion

Yottabyte (YB) 1 septillion

Storage Devices

Evaluating Storage

• Types of storage devices:– Hard drive– Floppy drive– Zip disk drive– CD/DVD– Flash memory

• Nonvolatile storage

Portable Storage

• Gives us the ability to move data from one computer to another

• Types of portable storage devices:– Floppy disk:

• Capacity 1.44 MB– Zip disk:

• Capacity 100 MB to 750 MB– CD-R, CD-RW, DVD-R, DVD-RW:

• Capacity 700 MB to 9.4 GB– Flash drive:

• Capacity 32 MB to 1 GB– Flash memory Card:

• Up to 4 GB

Storage Basics

• Storage Medium contains data

• A storage device records data and retrieves data on a storage medium– Data copied from storage device into RAM,

where it waits to be processed– Processed data is held temporarily in RAM

before copied to storage medium

WritingWritingProcess of transferring Process of transferring

items from memory items from memory to storage mediato storage media

WritingWritingProcess of transferring Process of transferring

items from memory items from memory to storage mediato storage media

Storage Device

• What is a storage device?

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ReadingReadingProcess of transferring Process of transferring

items from storage items from storage media to memorymedia to memory

ReadingReadingProcess of transferring Process of transferring

items from storage items from storage media to memorymedia to memory

Hardware that Hardware that records records

data data

Functions as source of input

Creates output

Access Time– Time required to deliver item from memory to processor

OR

– Time it takes storage device to locate item on storage medium

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• What is a hard disk?

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hard disk mountedin system unit

– High-capacity storage

– Consists of several inflexible, circular platters that store items electronically

– Components enclosed in airtight, sealed case for protection

Magnetic Disks

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•What are tracks and sectors?

Formatting prepares disk for use

Trackis narrow

recording bandthat forms fullcircle on disk

Sector stores up to512 bytes

of data

Magnetic Disks

• What are characteristics of a hard disk?

p. 359 Fig. 7-7 Next

Sample Hard Disk Characteristics

Advertised capacity 500 GB

Platters 4

Read/write heads 8

Cylinders 16,383

Bytes per second 512

Sectors per track 63

Sectors per drive 973,773,168

Revolutions per minute 7,200

Transfer rate 300 MB per second

Access time 8.5 ms

actualdisk

capacity

Hard Disk Drives: Long-Term Storage The hard disk permanently stores all your important data. Some hard disks can store more than 100 gigabytes of data.

RPM – Determines how fast your Hard Drive will access data. Revolutions Per Minute.

Typical RPM Values:

Desktop Machine – 7,200 RPMLaptop Machines – 5,000 RPMServer Machines – 10,000 RPM

Basic components of a hard drive

• Disk platters• Read/write heads• Head actuator• Spindle motor• Logic board• Cables & connectors• Configuration items (such as jumpers &

switches)

Spindle motor

• Motor that spins the platters

• Connected directly to the drive

Logic Boards

• Mounted on the hard drive

• Contain electronics that control the drive’s spindle & head actuator systems & present the data to the controller

Cables & Connectors

• Connectors for interfacing to the computer, receiving poweretc

Head disk Assembly

• Platters, spindle motor, heads, & head actuator mechanisms usually contained in this sealed chamber

Hard Disk Platters

• 3 1/2 inch drives are the most popular for desktop & some portables

• Max number of platters in a 3 1/2 inch drive is 11

Hard Disk Platters

• Traditionally made from aluminum alloy

• Desire for higher density has led to the use of platters made of glass (glass ceramic composite)– Glass platters offer greater rigidity & more

stable thermally

Hard Disk Platters

• No matter what type of platter is used, the platters are covered with a thin layer of magnetically retentive substance (called the medium) on which magnetic information is stored.– Oxide media– Thin-film media

Oxide media

• Made of various compounds, oxide being the primary active ingredient

• Put on the disk like syrup, coating the entire disk

• Coating is approx 30 millionths of an inch and is made smooth

• Platters appear to look brownish or amber

Oxide media

• Very sensitive to head-crash during movement of operation

• Very few drives use this technology anymore

Thin-film media

• Thinner, harder & more perfectly formed than oxide media

• Looks silver like the surface of a mirror .

Magnetic Disk

• Magnetic storage stores data by magnetizing microscopic particles on the disk or tape surface

Durability?

Read/Write Heads

• A hard disk has one read/write head for each side of the platter

• The heads are connected on a single movement mechanism

• They move in same manner and direction.

Read/Write Heads

• Each head is on an actuator arm that is spring-loaded to force the head into contact with a platter– The heads float only a very slight distance

above the platter

• When the drive is at rest, the heads are forced into direct contact with the platters by spring tension

Read/Write Heads

• Four types of read/write head designs:– Ferrite– Metal-In-Cap– Thin-film– Magneto-resistive

How a Hard Disk Works• Composed of several coated

platters stacked on a spindle

• Data saved to the disk: pattern of magnetized spots– Spots = 1– Spaces = 0

• Between platters are read/write heads that read and write magnetized data

• Spots are translated into data

Platters Read/write head

Access arms

The Hard DriveElectronic board

• Opening a hard disk ruins it.

• The electronics Integrated circuit controls the read and write mechanism and the motor that spins the platters.

• Turns bytes into magnetic domains and binary information accordingly

• May detach from the rest of the drive

The Hard Disk Drive

• Storage capacity up to 500 GB and more.

• Access time is measured in milliseconds

• Data transfer rate is measured in megabits or megabytes per second

• Spindle speed is measured in revolutions per minute (rpm)

Questions