Storage - Hard Drives and SSDs

Overview
You find yourself in a level that pits new vs. old, Hard Drives vs, SSDs. Can you keep sane as you try to distinguish the two as you travel to the next level? Only the observant and patient continue on.

Computer Disk

 * Example:
 * one bit -- a change in current polarity New_hard_drive.jpg
 * zero bit -- no change in polarity

Hard Drive

 * Hard Drive in Action
 * How a Hard Drive Works

Flash Memory

 * Invented in the 1980s, released to the commercial market in the 1990s
 * EEPROM chips
 * Electronically Erasable Programmable Read Only Memory Ssd.png
 * Used in
 * Increasingly, computer hard drives
 * Your computer's BIOS chip
 * CompactFlash (most often found in digital cameras)
 * SmartMedia (most often found in digital cameras)
 * Memory Stick (most often found in digital cameras)
 * PCMCIA Type I and Type II memory cards (used as solid-state disks in laptops)
 * Memory cards for video game consoles


 * Solid State
 * A control gate and a floating gate exchange electrons through an oxide layer.

Hard Disk vs. Flash

 * Flash memory is noiseless.
 * It allows faster access.thumb|300px|right
 * It is smaller in size.
 * It is lighter.
 * It has no moving parts.
 * Lower energy
 * Hard-drives are cheaper and have more capacity

Optical Storage

 * Short wavelength laser for read, write, and erase
 * The shorter the wavelength, the smaller the focused spot
 * Short wavelength=high frequency
 * Unlike magnetic recording, no contact between the medium and the heads

Eight to Fourteen Modulation (EFM)

 * Use 14-bit streams to represent 8-bit streams
 * Each 1 bit is separated by a minimum of two 0's and a maximum of ten consecutive 0's.
 * Eight-to-fourteen modulation conversion table
 * http://www.physics.udel.edu/wwwusers/watson/scen103/efm.html

Writing to Optical Storage

 * Organic dye Readlaser.png
 * material that can be “burned” by high heat
 * Magneto-optical
 * use magnetic polarity to alter light
 * Phase change
 * material that can be heated to change reflectivity

Compact Disks (CD)

 * CD-DA (digital audio)
 * CD-ROM (read only memory)
 * CD-R (recordable, but only once)
 * also called a WORM (write-once readmany) disk
 * CD-E (erasable); CD-RW (re-writable)
 * CD-V (video)
 * Disk can store 650 to 700 MB of data.

CD Encoding

 * CD-DA bit stream (pure audio)
 * max bandwidth of 20 kHz
 * sampling at 44.1 kHz
 * 16 bits/sample for left & right=32 bits/samp
 * 44.1 k X 32 = 1.41 Mbps
 * EFM (Eight to Fourteen Modulation )

Digital Versatile Disk (DVD)

 * 4.7GB in storage space Cddvd.png
 * Backward compatible with CD
 * Much more capacity than CD-ROM due to:
 * smaller pit length
 * tighter tracks
 * larger surface area utilization
 * more efficient channel bit modulation
 * more efficient error correction
 * less overhead
 * a single layer is about 7 times a standard CD-ROM

Regional Coding

 * Special code on on DVD movie read by player
 * limits playback to one of 6 regions
 * Exceptions (Region 0 discs): music, television programs, documentaries, specialist titles can be played in any DVD player

Blu Ray

 * 27GB of storage per layer Dvdblu.png
 * record high-definition television (HDTV) without any quality loss
 * instantly skip to any spot on the disc
 * record one program while watching another on the disc
 * create playlists
 * edit or reorder programs recorded on the disc
 * automatically search for an empty space on the disc to avoid recording over a program
 * access the Web to download subtitles and other extra features

Holographic Storage

 * 300GB - 1TB+ of storage
 * Blue-green argon laser Holographic-versatile-disc.jpg
 * Beam splitters to spilt the laser beam
 * Mirrors to direct the laser beams
 * LCD panel (spatial light modulator)
 * Lenses to focus the laser beams
 * Lithium-niobate crystal or photopolymer
 * Charge-coupled device (CCD) camera

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