Question 7A: Describe magnetic and optical storage media and how they are used. Give specific examples
Magnetic storage media
Magnetic storage and magnetic recording are terms from engineering referring to the storage of data on a magnetized medium. Magnetic storage uses different patterns of magnetization in a magnetizable
material to store data and is a form of non-volatile memory. The information is accessed using one or more read/write heads. As of 2013, magnetic storage media, primarily hard disks, are widely used to store computer data as well as audio and video signals. In the field of computing, the term magnetic storage is preferred and in the field
of audio and video production, the term magnetic recording is more commonly used. The distinction is less technical and more a matter of preference. A hard disk contains one or more inflexible, circular platters that use magnetic particles to store data, instructions, and information. Hard disks can store data using longitudinal recording or perpendicular recording. Formatting is the process of dividing the disk
into tracks and sectors so that the operating system can store and locate data and information on the disk. The hard disk arms move the read/write head, which reads items and writes items in the drive which location often is referred to by its cylinder. A head crash occurs when a read/write head touches the surface of a platter so always keep a backup of your hard disk. RAID (redundant array
of independent disks) is a group of two or more integrated hard disks.A network attached storage (NAS) device is a server connected to a network with the sole purpose of providing storage. An external hard disk is a separate free- standing hard disk that connects to your computer with a cable or wirelessly. A removable hard disk is a hard disk
that you insert and remove from a drive. Internal and external hard disks are available in miniature sizes (miniature hard disks). A disk controller consists of a special-purpose 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 of the computer.
Characteristics
of a hard disk include:
capacity -number of bytes the storage medium can hold.
platters -made of aluminium glass,
or ceramic and coated with an alloy material that allows items to be recorded magnetically on its surface.
read/write head -mechanism that reads items and writes items in the drive as it barely touches the disk's recording surface.
cylinder -vertical section of a track that passes through all platters.
sectors -storage location; pie-shaped; breaks the tracks into arcs.
tracks - narrow recording band; forms a full circle on the surface of the disk.
revolution per minutes - measurement of the frequency of
a rotation. It annotates the number of turns completed in one minute around a fixed axis. It is used as a measure of rotational speed of a mechanical component.
transfer rate -the speed with which data, instructions, and
information transfer to and from a device; stated in KBps and MBps.
access time -measurement of the amount of time it takes a storage device to locate an item on a storage medium.
Other examples of magnetic storage media include magnetic recording
tape, and magnetic stripes on credit cards.
Magnetic recording tape - a magnetically coated ribbon of plastic capable of storing large amounts of data and information. A tape drive reads and writes data and information on a tape.
Magnetic
stripe card - contains a magnetic stripe that stores information.
Optical storage media
An optical disc consists of a flat, round, portable disc made of metal, plastic, and lacquer that is written and read by a laser. Typically store software, data, digital photos, movies, and music. Read only vs. rewritable. Optical discs commonly store items in a single track that spirals from the centre of the disc to the edge. Track is divided into evenly sized
sectors. A CD-ROM can be read from but not written to. Read from a CD-ROM drive or CD-ROM player. A CD-R is a multi-session optical disc on which users can write, but not erase. A CD-RW is an erasable multi-session disc. Must have a CD-RW drive. Optical disc has 2 types of disc. The two types of optical disc are archive disc and picture CD.
Archive disc
Stores photos from an online photo centre.
Resolution usually is 7200 pixels per photo.
Cost is determined by the
number of photos being stored.
Picture CD
Single-session CD-ROM that stores digital versions of film.
Typically uses a 1024 x 1536 resolution.
Many photo centres offer Picture CD services.
A DVD-ROM is a
high-capacity optical disc on which users can read but not write or erase. It requires a DVD-ROM drive. A Blu-ray Disc-ROM (BD-ROM) has a storage capacity of 100 GB. DVD-RW, DVD+RW, and DVD+RAM are high-capacity rewritable DVD formats.
