Chapter 7 – Storage - Review How Are Storage Devices Different from Storage Media? A storage medium is the physical material on which a computer keeps data, instructions, and information. The number of bytes (characters) a storage medium can hold is its capacity. A storage device is the computer hardware that records and/or retrieves items to and from storage media. Writing is the process of transferring items from memory to a storage medium, and reading is the process of transferring these items from a storage medium into memory. What Are the Characteristics of an Internal Hard Disk? A hard disk, also called a hard disk drive or hard drive, is a storage device that contains one or more inflexible, circular platters that use magnetic particles to store data, instructions, and information. Traditionally, hard disks stored data using longitudinal recording, which aligned the magnetic particles horizontally. With perpendicular recording, hard disks align the particles vertically, making much greater storage capacities possible. The capacity of a hard disk is determined from whether it uses longitudinal or perpendicular recording, the number of platters it contains, and the composition of the magnetic coating on the platters. A platter is made of aluminum, glass, or ceramic and is coated with a material that allows items to be recorded magnetically on its surface. Each platter has two read/write heads, one for each side. The location of a read/write head often is referred to by its cylinder, which is the vertical section of a track that passes through all platters. Formatting is the process of dividing the disk into tracks and sectors. A track is a narrow recording band that forms a full circle on the surface of the disk. The disk's storage locations are divided into pie-shaped sections, which break the tracks into small arcs called sectors. While the computer is running, the platters in the hard disk rotate at 5,400 to 15,000 revolutions per minute (rpm), which allows nearly instant access to all tracks and sectors on the platters. Transfer rate is the speed with which data, instructions, and information transfer to and from a storage device. Access time measures the amount of time it takes a storage device to locate an item on a storage medium, or the time required to deliver an item from memory to the processor. What Is the Purpose of Network Attached Storage Devices, External and Removable Hard Disks, and Hard Disk Controllers? A network attached storage (NAS) device is a server connected to a network with the sole purpose of providing storage. NAS devices often use a RAID configuration. An external hard disk is a separate free-standing hard disk that connects with a cable to a USB or FireWire port on the system unit or communicates wirelessly. External hard disks have storage capacities up to 4 TB and more. A removable hard disk can be inserted or removed from a built-in or external drive. Removable hard disks have storage capacities up to 750 GB. A disk controller consists of a specialpurpose chip and electronic circuits that control the transfer of data, instructions, and information from a disk to and from the system bus and other components in a computer. A hard disk controller may be part of the hard disk on the motherboard, or it may be a separate adapter card inside the system unit. What Are the Various Types of Flash Memory Storage? Flash memory chips are a type of solid state media, which means they consist entirely of electronic components and contain no moving parts. A solid state drive (SSD) typically uses flash memory to store data, instructions, and information. A memory card is a removable flash memory device that you insert and remove from a slot in a computer, mobile device, or card reader/writer. Common memory cards include CompactFlash (CF), Secure Digital (SD), Secure Digital High Capacity (SDHC), microSD, microSDHC, xD Picture Card, Memory Stick, and Memory Stick Micro (M2). A USB flash drive, sometimes called a thumb drive, is a flash memory storage device that plugs in a port on a computer or mobile device. An ExpressCard module is a removable device that fits in an ExpressCard slot. ExpressCard modules can add memory, storage, communications, or other capabilities to a computer. What Is Cloud Storage, and What Are Its Advantages? Cloud storage is an Internet service that provides storage for computer users. Available for all sizes of users, with various degrees of storage services available for home and business users, cloud storage fees vary, depending on the user's storage requirements. Advantages include accessing files on the Internet from any computer or device with Internet access; storing large audio, video, and graphics files on the Internet instantaneously; allowing others to access their files on the Internet; viewing time-critical data and images immediately; storing off-site backups of data; and providing data center functions. Chapter 7 – Storage - Review What Are the Characteristics of Optical Discs? An optical disc is a type of storage media that consists of a flat, round, portable disc made of metal, plastic, and lacquer that is written and read by a laser. Optical discs, which primarily store software, data, digital photos, movies, and music, contain microscopic pits (indentations) and lands (flat areas) in their middle layer. Optical discs commonly store items in a single track that spirals from the center of the disc to its edge. Like a hard disk, the single track is divided into evenly sized sectors. How Are the Various Types of Optical Discs Different? A CD-ROM, or compact disc read-only memory, is a type of optical disc that uses laser technology to store items. Users can read the contents of standard CD-ROMs but cannot erase or modify their contents. A CD-R (compact discrecordable) is a multisession disc on which users can record their own items, such as text, graphics, and audio. Each part of a CD-R can be written on only one time, and the disc's contents cannot be erased. A CD-RW (compact discrewritable) is an erasable disc that can be written on multiple times. An archive disc stores photos from an online photo center in the jpg file format. A Picture CD is a single-session CD-ROM that stores digital versions of film using the jpg format at a lower resolution than an archive disc. A DVD-ROM (digital versatile disc-read-only memory or digital video disc-read-only memory) is a high capacity optical disc that you can read but not write on or erase. A newer, more expensive DVD format is Blu-ray Disc-ROM (BD-ROM), with higher capacity and better quality than standard DVDs. Many types of recordable and rewritable DVD formats are available. DVD-R and DVD+R are DVD-recordable formats. BD-R is a high-capacity DVD-recordable format. DVD-RW, DVD+RW, and DVD+RAM are rewritable DVD formats that allow users to erase and record multiple times. BD-RE is a high-capacity rewritable DVD format. How Are Tape, Magnetic Stripe Cards, Smart Cards, Microfilm and Microfiche, and Enterprise Storage Used? Tape is a magnetically coated ribbon of plastic capable of storing large amounts of data and information at a low cost. A tape drive reads and writes data and information on tape. Business users utilize tape most often for long-term storage and backup. A magnetic stripe card is a credit card, entertainment card, bank card, or other similar card with a stripe that contains information identifying you and the card. A magnetic stripe card reader reads the information stored on the stripe. A smart card, which is similar in size to a credit or ATM card, stores data on a thin microprocessor embedded in the card. A smart card reader reads the information on the smart card and updates it if necessary. Microfilm is a 100- to 215-foot roll of film. Microfiche is a small sheet of film, usually about 4 X 6 inches. Microfilm and microfiche reduce the amount of paper firms must handle, are inexpensive, and have the longest life of any storage media. Enterprises use computers, servers, and networks to manage and store huge volumes of data and information. In an enterprise, some storage systems can provide more than 185 TB of storage, and optical disc servers hold hundreds of optical discs.
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