Storing Data: Electronic Filing Cabinets
What You Will Learn
Difference between memory and storage
How storage media are categorized
Measuring a storage device’s performance
How data is stored on hard and floppy disks
Characteristics of hard drives
Uses of removable disks
Various optical storage media
New storage media
What is the difference between memory and storage?
Storage devices hold programs and data in units called files
Files are stored in directories or folders
Memory is a temporary workplace where the computer transfers the contents of a file while it is being used
Hard Drive RAM memory
Why is storage necessary?
Storage retains data when the computer is turned off
Storage is cheaper than memory
Storage plays an important role during startup
Storage plays an input role when starting applications
Storage is needed for output
Storage devices can hold a large amount of data
What is a storage device?
Hardware that is capable of retaining data when electricity is turned off
Able to read (retrieve) data from a storage medium (disk/tape)
Able to write (record) data to a storage medium
What are the types of storage technologies?
Sequential- Hardware that reads and writes data in a serial (one after the other) fashion
Random Access- Hardware that reads and writes data without going through a sequence of locations
Magnetic- Hardware that uses disks or tapes that are coated with magnetic material
Optical- Hardware that uses laser beams to read data from plastic disks
Solid State- Devices that use nonvolatile memory chips to read and write data
Sequential – Magnetic Storage
Random Access – Magnetic Storage
Tape Backup Unit
Floppy Drive Hard Drive Jaz Drive Zip Drive
Sequential – Optical Storage
CD ROM / DVD Drive
Magnetic – Optical Storage
Magneto-Optic (MO) Drive
Solid State Storage
Compact Flash Memory
Flash Memory
Smart Card
Micro Drive
Memory
Stick
PC Card
How is a storage device’s performance measured?
Capacity- The number of bytes of data that a device can hold
Access Time- The amount of time it takes for the device to begin reading data; measured in milliseconds (ms)
Floppy Disk
Hard Drive CD ROM / DVD
Capacity- 720KB to 1.44 MB
Access Time- 100ms
Capacity- Up to 80 GB
Access Time- 6 to 12ms
Capacity- CD Rom 650MB; DVD 17GB
Access Time- 80 to 800ms
What are hard disk drives?
A high speed, high capacity storage device
Consists of metal disks called platters
Contains two or more stacked platters with read/write heads for each side
Works similarly to floppy disk drives
What affects a hard disk’s performance?
Seek time or positioning performance- How quickly the read/write head positions itself and begins transferring information. Measured in milliseconds (ms)
Spindle speed or transfer performance- How quickly the drive transfers data. Measured in rotations per minute (RPM)
What are hard disk interfaces?
Enables the hard disk to communicate with the CPU by way of the hard disk controller
Types of interfaces
Integrated Drive Electronics (IDE)- also called ATA or IDE/ATA
Serial ATA interfaces, also known as SATA150
Small Computer System Interface (SCSI)
FireWire/IEEE 1394
What is a removable hard disk?
Platters are enclosed in a cartridge which can be inserted or removed from a drive
Used for data archiving and data backup
Usually connected via USB
Jaz Drive
What is a tape backup unit?
A device used to store large amounts of data that are not used frequently
Uses cassette type reel to reel plastic tape
Tape Backup Unit
What is a CD-ROM?
Stands for compact disk-read only memory
CD-ROM drives can not write data to disks
Capable of storing 700MB of data
Used for storing operating systems, large application programs, and multimedia programs
How does a CD-ROM drive work?
Laser beams read microscopic patterns of data on the disk’s surface
Disks contain indentations (pits) and flat reflective areas (land)
The computer interprets the pits as 0’s and the lands as 1’s
What is CD-R and CD-RW?
CD-R
Disks that can be read and written to
Disks can only be written to “once”
Drives that are capable of reading and writing data
CD-RW Disks that can be read and written to
Disks are erasable
Disks can be written to many times
Drives that are capable of reading, writing and erasing data
What is DVD?
Stands for digital video disk
Uses similar technology as CD-ROM
Capable of storing up to 17GB of data
Data transfer rate comparable to hard disk drive
Compatible with CD-ROM disks
DVD-RAM- Ability to read/write data
What is solid state storage?
Nonvolatile memory chips used to retain data
Solid state storage devices do not have moving parts
Solid state storage devices are small, lightweight, reliable, and portable
Types of solid state storage devices
PC or PCMCIA card- Credit card sized device used mainly with notebook computers; Various functions (modem, adapter, memory and storage)
Types of solid state storage devices
Flash memory card- Wafer thin card used with cellular phones, MP3 players, and digital cameras
Types of flash memory cards- SmartMedia card, CompactFlash card, and Sony’s Memory Stick
CompactFlash Memory StickSmartMedia
Types of solid state storage devices
Smart card- Credit card sized device combining flash memory with a microprocessor; Used as a credit card; Has more functionality, convenience, and safety than credit cards
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