Chapter 8 Digital Storage
Storage
Long term
Permanent access data & information
Location keeps programs & applications
Storage Medium
Secondary storage
Non - volatile
Memory
Contrast, holds data & instruction temporarily
Volatile
Exp : RAM
Storage media
Exp
Cloud storage
Storage hardware
Hard Disks Drive ( HDD )
Solid - State drives ( SSD )
Memory cards
USB flash drives
Optical discs
Tags
Keep information on servers on Internet
Physical material
Keep data, information, program, application
Actual online storage media
Transparent to user
Storage device
Record / retrives items to & from storage media
Reading
Process - transferring items from storage medium into memory
Writing
Process - transferring items from memory to storage medium
Storage Technologies
NFC tag
Smart card
Optical disc
Memory card
USB flash drive
External hard drive
Hard disk drive
Storage Capacity
Capacity - Number of bytes a storage medium can hold
Term
Kilobyte ( KB ) = 1 thousand
Megabyte ( MB ) = 1 million
Gigabyte ( GB ) = 1 billion
Terabyte ( TB ) = 1 trillion
Access time
Measure
Amount of time it takes storage device to locate an item
Time required to deliver an item from memory to processor
Faster Transfer rate
Memory ( most RAM )
Slower transfer rate
SSDs
Hard Disks
USB flash devices
Memory cards
Optical discs
One / more inflexible, circular platters
Use magnetic particles to store data, instructions, information
Platter
Spindle
Head
Actuator arm
Actuator axis
Power connector
Jumper block
Actuator
Characteristics
Tracks 轨道
Sectors 区域
Platters
Form factor 大小
Read / write head
Revolutions per minute 时间
Form factor
Modern HDDs
Desktop computers - 3.5 - inch
Laptops - 2.5 - inch
Store data
More platter can keep more storage
Higher density can have more files & storage
Depends how they do recording
Density
How close the data from one to another
Talk about closeness
Further away cannot have more files & storages
Longitudinal recording
Perpendicular reading
can save more files & storage
can record more data
Platter
Formatting - Process of dividing the disk into tracks & sectors
Interface cables
IDE ( Integrated Device Electronic )
SATA ( Serial Advanced Technology Attachment )
SCSI ( Small Computer System Interface )
Serial Attached SCSI ( SAS )
USB ( Universal Serial Bus )
Transfer Rate
Fast
Slow
Exp : Type C
The lowest the slowest
The highest the faster
R / W ( Read and Write )
Head crash
Read / write head touches surface of platter
Always keep backup of hard disk
RAID ( Redundant Array of Independent Disks )
Group of two / more integrated HDD
Without RAID
With RAID
Purpose
Improve speed in file retrieval
Back - up large amount of data
Ease of managing hard disks
Separate free - standing storage device
Connect with cable to USB port
Flash memory chips
Solid state media
No moving part
9 Advantages
Inside of SSD
Case of internal SSD
External SSD
Internal SSD inserted into laptop
Flash memory card
Small removable storage
Insert & remove from a slot
Digital camera
Smartphone
Printer
Card reader
Laptop
Tablet
USB Flash memory drive
AKA Thumbdrive / flash drive
Plug into USB port
Optical discs
Flat, round, portable disc
Metal, plastic
Lacquer
Write & read by laser
Store items in single track that spirals from center / edge of the disc
Track divided into evenly sized sector
Disc sectors
Single tracks spirals to edge of disk
CD - ROM
Can read X written 只能读不能写
Single - session disc
CD - R
Write once X erase 只能写一次 不能改
CD - RW
Erasable multisession disc 能改很多次
DVD - ROM
DVD - R
DVD + R
DVD - RW
DVD + RW
DVD + RAM
High capacity
High - capacity rewritable
DVD - recordable WORM formats
Enterprise storage server
Large organization
Manage & storage data & information using
Heavy use, maximum efficiency, maximum availability
RAID
Duplicates data, instructions, information - improve data reliability
Network Attached Storage ( NAS )
Server - placed network with sole purpose of providing storage to users, computers, devices attached to network
Storage appliance
Own IP address
Not have keyboard / display
Have at least one hard drive
Often configured in a RAID
Storage Area Network ( SAN )
High - speed network
Sole purpose of providing storage to other attached servers
Tape storage
Magnetically coated ribbon of plastic capable of storing large amounts of data & information
Read & write data & information on tape
Other Type of storage
Magnetic stripe in smart card
Magnetic stripe stores information
Smart card
Store data on microchip embedded in card
RFID tag
Consists antenna
Mmory chip contains information to transmitted via radio waves
RFID reader
Reads radio signal
Transfers information
Microfilm & Microfiche
Store microscopic images of documents on roll / sheet film
NFC
Technology ( based on RFID )
Close - range radio signals
Transmit data between 2 NFC - enabled devices / NFC enabled device & NFC tag
NFC - enabled devices
NFC chip
NFC tag
Self - adhesive
Attached to any location
Cloud storage
Internet service - provide storage to computer / mobile device users
Cloud computing
Front end ( Hardware & Software )
Back end ( Server & Storage device )
Connect to each other through network
SaaS ( Software as a service )
Consumers & organizations rely on cloud computing services to manage
Infrastructure as a service ( IaaS )
Storage as service ( STaaS )
Desktop as a service
Platform as a service ( PaaS )
Additional cloud services
Synchronize files
Write documents
Backup files
Stream media
Multiple hard disk
Faster
Chip put in card