Secondary Storage Chapter 7

Introduction Data storage has expanded from text and numeric files to include digital music files, photographic files, video files, and much more. These new types of files require secondary storage devices with much greater capacity. In this chapter, you learn about the many types of secondary storage devices including their capabilities and limitations.

Storage Primary storage Secondary storage Volatile storage Temporary storage Random Access Memory (RAM) Secondary storage Nonvolatile storage Permanent storage Secondary storage characteristics Media Capacity Storage devices Access speed Primary storage (key term) temporary storage Secondary storage (key term) permanently saves information for future use; to share information with others; to modify at later date using secondary storage devices (key term) Secondary storage is nonvolatile – stores programs and data as opposed to temporary storage (RAM) Characteristics include: Media or medium (key term) – actual physical materials that holds the data and programs Capacity (key term) – measures how much a particular storage medium can hold Storage devices (key term) – hardware that reads data and programs from storage media (most also write to storage media) Access speed (key term) – measures the amount of time required by the storage device to retrieve data and programs Writing– process of saving information to the secondary storage device Reading – process of accessing information from secondary storage

Important characteristics of secondary storage Media are the actual physical material that holds the data and programs. Capacity measures how much a particular storage medium can hold. Storage devices are hardware that reads data and programs from storage media. Most also write to storage media. Access speed or access time measures the amount of time required by the storage device to retrieve data and programs.

Hard Disks Save files by altering the magnetic charges of the disk’s surface to represent 1s and 0s. Retrieve data and programs by reading the charges from the magnetic disk.

Hard Disks Density refers to how tightly these charges can be packed next to one another on the disk. Rigid metallic platters that are stacked one on top of another. Store and organize files using tracks, sectors, and cylinders. Tracks are rings of concentric circles without visible grooves. Each track is divided into invisible wedge-shaped sections called sectors. A cylinder runs through each track of a stack of platters. Cylinders are necessary to differentiate files stored on the same track and sector of different platters.

Hard Disks A head crash occurs when a read/write head makes contact with the hard disk’s surface or with particles on its

Performance Enhancements Disk caching Redundant arrays of inexpensive disks (RAID) File compression and file decompression

Optical Discs A laser beam alters the surface of a plastic or metallic disc to represent data. Optical discs use reflective light to represent data. The 1s and 0s are represented by flat areas called lands and bumpy areas called pits on the disc surface. Disc is read by an optical disc drive using a laser that projects a tiny beam of light on these areas. The amount of reflected light determines whether the area represents a 1 or a 0.

Compact Disc Store 700 MB (megabytes) of data on one side of a CD. Three basic types of CDs: Read only—CD-ROM - cannot be written on or erased by the user. Write once—CD-R - can be written to once. Rewriteable—CD-RW – can be written to many times.

Digital Versatile Disc (DVD) DVD stands for digital versatile disc or digital video disc Can store 4.7 GB (gigabytes) on one side of a DVD disc Capacity is 17 times that of a CD. Three basic types of DVDs: Read only—DVD-ROM - cannot be written on or erased by the user. Write once— DVD+R, DVD-R - can be written to once. Rewriteable— DVD+RW, DVD-RW, DVD-RAM – can be written to many times.

Blu-ray Disc Have a greater capacity than DVDs. The hi def standard is Blu-ray Disc (BD). Blu-ray Discs have a capacity of 50 GB on one side Capacity is 10 times that of a standard DVD. Three basic types of Blu-ray: Read only—BD - cannot be written on or erased by the user. Write once—BD - can be written to once. Rewriteable—BD – can be written to many times.

Solid-State Storage Solid–state drives (SSDs) Flash memory cards No moving parts Faster and more durable than hard disks Flash memory cards Widely used in computers, cameras, and portable devices such as mobile phones and GPS navigation systems USB Drives (or Flash Drives) Connect to USB port Capacity of 1 GB to 256 GB Solid state drives (key term) are faster and more durable (no moving parts) than hard drives Require less power Contain solid state memory instead of magnetic disk to store data Used for tablet PCs, like the iPad Flash memory cards (key term) are one type of solid state device. Used in digital cameras, ipods USB Drives (key term) or Flash drives (key term) connect to a USB port

Cloud Computing Cloud computing is where the Internet acts as a “cloud” of servers Applications provided as a service rather than a product Supplied by servers Google Apps Mint.com Cloud computing (key term) is where the Internet provides cloud storage (key term) also know as online storage (key term) The processing power of the service provider’s server is used to run the applications and your computer is responsible only for displaying the results. The applications and data can be accessed from any Internet-ready device. This means that devices with little storage, memory, or processing power, such as mobile phones, can run the same powerful applications as a desktop computer. Cloud servers provide storage, processing, and memory. Software installation and upgrades are avoided.

Cloud Storage Services

Making IT Work for You ~ Cloud Storage Using a cloud storage service makes it easy to upload and share files with anyone.

Mass Storage Devices Large amounts of secondary storage called mass storage An enterprise storage system strategy ensures efficient and safe use of data across an organizational network Devices include: File servers Networked attached storage (NAS) RAID systems Tape libraries Organizational cloud storage Mass storage devices (key term) are designed to meet the demands for a tremendous amount of mass storage (key term). Support enterprise storage systems are File servers (Key Term) – dedicated computer with very large storage capacities that provide user access to fast storage and retrieval of data Network attached storage (NAS) – similar to a files server except less expensive RAID systems (Key Term) – larger versions of the specialized devices discussed earlier in this chapter that enhance organizational security by constantly making backup copies of files moving across the organization’s networks Tape library (Key Term) – device that provides automatic access to data archived on a large collection or library of tapes Organizational cloud storage (key term) – high speed internet connection to a dedicated remote organizational cloud storage server.

Mass Storage Devices File servers—dedicated computers with very large storage capacities that provide users access to fast storage and retrieval of data. Network attached storage (NAS) – similar to a file server except simpler and less expensive; widely used for home and small business storage needs.

Mass Storage Devices RAID systems—specialized devices hat enhance organizational security by constantly making backup copies of files moving across the organization’s networks. Tape library—device that provides automatic access to data archived on a large collection or library of tapes. Organizational cloud storage - high-speed Internet connection to a dedicated remote organizational Internet drive site.

Enterprise Storage Systems

Storage Area Network (SAN) Architecture to link remote computer storage, such as enterprise storage systems, devices to computers such that the devices are available as locally attached drives User’s computer provides file system, but SAN provides disk space House data in remote locations and still allow efficient and secure access Storage area network (SAN) (key term) – a recent mass storage development.