Chapter 6

Storage: Holds data, instructions and information for future use.Storage medium: also known as secondary storagePhysical material on which a computer keeps data, instructions and informationStorage device: the computer hardware that records and/or retrieves items to and from storage mediaReading: process of transferring these items from storage medium into memoryWriting: process of transferring data, instructions and information from memory to a storage medium.

Storage TermApproximate No of BytesExact Number of BytesKilobyte (KB)1 thousand210 or 1,024Megabyte (MB)1 million220 or 1,048,576Gigabyte (GB)1 billion230 or 1,073,741,24Terabyte (TB)1 trillion240 or 1,099,511,627,776Petabyte (PB)1 quadrillion250 or 1,125,899,906,842,624Exabyte (EB)1 quintillion260 or 1,152,921,504,606,846,976

Capacity: the number of bytes a storage medium can holdAccess time: measures:The amount of time it takes a storage device to locate an item on a storage mediumThe time required to deliver an item from memory to the processor.Transfer rate: the speed with which data, instructions and information transfer to and from a device.Affects access time; KBps, MBps, GBps

Storage devices are slow compared with the access time of memoryMemory chips access items in billionths of a second (nanoseconds)Storage devices access items in thousandths of a second (microseconds)

Hard disk drive or hard driveStorage device that contains one or more inflexible, circular platters that use magnetic particles to store data, instructions or informationCurrent PC hard disk storage capacities ranges from 160 GB to 3 TBAccess time is 8.5 ms.

External hard diskRemovable hard diskA separate freestanding hard disk that connects with a cable to a USB port or FireWire port on the system unit or communicates wirelessHard disk that you insert and remove from a drive.

Redundant Array of Inexpensive DisksA storage system that links any number of disk drives so that they act as a single disk.An ideal solution for user who must have the data available when they attempt to access it.

Three common techniques used:Striping (RAID 0), provides the user with rapid access by spreading data across several disks.Mirroring (RAID 1), data is written to two or more disks simultaneously, providing a complete copy of all the information on multiple drives in the event one drive should failStriping with parity (RAID 4), data is spread over multiple disks. Provides the speed of striping with the safety of redundancy because the system stores parity information that can be used to reconstruct data if a disk drive fails.

Server connected to a network with the sole purpose of providing storageAny user or device connected to the network can access files on the NAS device.

Consist entire of electronic components such as IC and contain no moving parts.More durable and shock resistant than other types of mediaCapacity ranges from 16 GB to 256 GBAccess time is about 0.1 ms, which is more than 80 times faster than a hard disk.

Enable users easily to transport digital photos, music or files to and from mobile devices and computers or other devices.Various Types:Secure Digital (SD)microSDxD Picture cardMemory stick PRO Duo

A flash memory storage deviceMakes it easy for users to transfer documents, photos, music and videos from one computer to another.

Removable device commonly used in notebook computers.

An Internet service that provides storage to computer users.Some provide storage for specific types of files where others store any type of fileExamples:Flicker, Picasa stores digital photosFacebook, myspace digital photos, digital videos, messages, personal informationGoogle Docs documents, spreadsheets, presentationsGmail E-mail messagesYoutube-Digital videosAmazon EC2, Amazon S3, Nirvanix Enterprise-level storage

A newer, more expensive DVD formatHas higher capacity and better quality than standard DVDs especially for high-definition audio and video.BD ROM has storage capacities of 100 GB

Magnetically coated ribbon of plastic capable of storing large amounts of data and information at a low cost.Business users utilize tape most often for long-term storage and backup.

Stores digital images on the filmThe stored images are so small that you can read them only with a microfilm reader.Used by libraries to store back issues of newspapers, magazines and genealogy recordsHave the longest life of any storage media

Use computers and computer networks to manage and store huge volumes of data and information about customers, suppliers and employees.One or more servers on the network have the sole purpose of providing storage to connected users.