Presentation On Hard Disk

Presentation on Hard disk

Storage • What is storage? • Holds data, instructions, and information for future use  Storage medium is physical material used for storage

Next

Storage Capacity –

Number of bytes (characters) a storage medium can hold

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 Next

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

Storage Device • What is a storage device? Reading Process of transferring items from storage media to memory

Hardware that records data

Functions as source of input

Writing Process of transferring items from memory to storage media

Creates output Next

Access Time –

Time required to deliver item from memory to processor OR

–

Time it takes storage device to locate item on storage medium

Next

hard disk mounted in system unit

• What is a hard disk? – High-capacity storage – Consists of several inflexible, circular platters that store items electronically – Components enclosed in airtight, sealed case for protection Next

Magnetic Disks •What are tracks and sectors? Track is narrow recording band that forms full circle on disk

Sector stores up to 512 bytes of data Formatting prepares disk for use Next

Magnetic Disks • What are characteristics of a hard disk?

Sample Hard Disk Characteristics Advertised capacity Platters Read/write heads Cylinders Bytes per second Sectors per track Sectors per drive Revolutions per minute Transfer rate Access time

p. 359 Fig. 7-7

500 GB 4 8 16,383 512 63 973,773,168 7,200 300 MB per second 8.5 ms

actual disk capacity

Next

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 RPM Laptop Machines – 5,000 RPM Server 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

Platters

– Spots = 1 – Spaces = 0

• Between platters are read/write heads that read and write magnetized data • Spots are translated Access arms into data

Read/write head

The Hard Drive Electronic 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