Understanding Computer Storage: Secondary vs. Primary, Types, and Factors to Consider, Study notes of Technology

Download Understanding Computer Storage: Secondary vs. Primary, Types, and Factors to Consider and more Study notes Technology in PDF only on Docsity! COMPUTER STORAGE DEVICES A storage device records and retrieves items to and from a storage medium. A storage media is the actual physical material that holds data and programs. Writing is the process of saving information to storage devices whereas reading is the process of accessing information from storage devices. Writing of data = storing data also known as saving-Reading of data = getting our data back also known as opening. To save data, data is moved from memory to secondary storage. Factors to consider when choosing a storage device 1) Storage capacity 2) Brand/make 3) Portability 4) Durability/readability 5) Price/cost 6) Compatibility with system-IDE, USB, SATA 7) Safety of the media/nature of work to be stored 8) Data access speed How Are Backups Created? 1)Burning files to a CD 2)Copying files to an external hard-drive 3)Copying the files to another computer on a network Forms of computer storage 1) Secondary storage (backing storage or auxiliary storage) 2) Primary storage (memory) Secondary storage Secondary storage is a type of storage designed to retain data and instructions in a relatively permanent form. Secondary storage devices are storage devices designed to retain data and instructions in a relatively permanent form. Secondary storage devices can be used as both input (when part of their stored data is sent for processing) and output devices (when used to receive processed data) Magnetic storage devices 1) Floppy diskette 2) Magnetic tape 3) Zip disk 4) Jaz disks 5) Hard disk Optical storage devices 1) Compact disks (CD) 2) Digital video disks (DVD) Solid state storage devices 1) Memory cards 2) Smart cards 3) Flash disks Care for floppy diskettes 1) Keep the diskettes in a storage tray or protective case when not in use 2) Do not place heavy objects on the diskettes 3) Keep diskettes away from direct sunshine or excessive heat. 4) Do not use floppy diskettes near magnetic fields since data can be lost. 5) Do not use alcohol to clean the floppy diskette. 6) Do not use rubber bands or paper clips to tie the floppy diskettes together. 7) Diskettes should not be bent or sat on to avoid breaking them 8) The circular disk surface should not be touched since it is easily contaminated which can lead to data loss. Advantages of using floppy diskettes 1) Can be used to transfer data from one computer to another 2) Are portable and inexpensive 3) Data on a floppy disk can be accessed randomly. 4) Data on a floppy disk can be write-protected from being changed accidentally using the write protection tab. Disadvantages of floppy diskettes 1) Floppy diskettes are not durable since they can be destroyed by dust and dirt, magnetic fields. 2) Access time of a floppy is slow 3) Storage capacity of a floppy disk is limited Before anything can be written on a new floppy disk, it must be formatted. Formatting is the process of preparing a disk for reading and writing by organizing the disk into storage locations. The write protect facility is useful to prevent accidental overwriting of data. Zip disks Another obsolete storage device, Zip disks are high capacity disks that resemble floppy disks however are slightly larger and thicker is size compared to floppy disks. Zip disks were used for data backup and moving large files between computers. Jaz disks These are small portable disks with high storage capacity and are used for storing data that requires large storage. Jaz disks were used for data backup and moving large files between computers. Were expensive and very unreliable. Hard disks A hard disk usually consists of several inflexible circular magnetic disks called platters on which data, instructions and information are stored electronically. A hard disk is also known as a hard disk drive (HDD). Hard disks are sealed tightly to keep out contaminants like dust and smoke which can lead to head crashes. Hard disks are used to: 1) Data and files 2) Application software 3) System software like the operating system Uses of external hard disks 1) Can carry data-backups all over the place 2) Transfer information, programs and pictures between computers Advantages of external hard disks 1) Improved data cargo carrying capacity 2) More portable-small and light Disadvantages of external hard disks 1) Have to be handled quite carefully 2) More expensive than other forms of removable storage. 3) Easy to be stolen or misplaced Removable storage media Removable media is any type of storage device that can be removed from a computer and is not incorporated into the computer itself. Examples of removable media include CDs, DVDs and Blu-Ray disks, as well as diskettes and USB drives. Removable media makes it easy for a user to move data from one computer to another and can deliver the fast data backup and recovery times The main drawback of removable media is that it's more expensive than many other forms of storage. b) Solid state storage devices Solid state storage devices are devices with no moving parts. Data and information are stored and retrieved electronically directly from these devices. This type of storage is expensive but is more reliable and requires less power and can be written to and updated. This technology is becoming widely used for specialized removable storage devices. Flash disks Flash disks are small storage devices that can be held on a key ring or necklace. These devices conveniently connect directly to a computer’s universal serial bus port to transfer data, files and information. Flash disks are used: 1) When there is need to access files on various electronic devices with USB ports 2) When files have to be kept for a long time (quickly and easily backup files) 3) When more files have to be added from time to time 4) When there is need create a boot disk Advantages of flash disks 1) More compact and durable shape, design 2) Hold much more data 3) Operate more reliably due to no moving parts 4) Compatible with almost any computer Disadvantages of flash disks 1) No write protection feature so it is possible to accidentally copy over data 2) Small physical size means that they are easy to misplace or lose 3) More expensive per unit of data stored compared to hard disks c) Optical storage devices Optical storage devices store data on a disk as a number of data dots that can be read using light. Data is read by shinning the laser beam onto the surface of the disk. The beam burns very tiny holes (pits) into a thin shiny surface to record data. Care for optical disks 1) Do not leave the disks in direct sunlight or in hot, humid conditions. 2) Use a soft lint free cloth to remove spots, dust or finger prints and smears on the disk. 3) Store the disks in protective cases 4) Never stack disks on top of each other 5) Never touch the underside of the compact disk 6) Handle the disks only by the outer edges to prevent finger prints and smears on the disks Advantages of optical disks 1) Are easy to store and are portable 2) Have high storage capacity of over 700MB 3) Are durable and can be stored for a long period of time. 4) Have high access speed and reduces access time 5) Can store text, graphics, video and sound as well as games. Disadvantages of optical disks 1) Breakage or a simple scratch may render the whole disk useless. 2) Can be attacked by viruses 3) Some kinds of compact disks are read only so their contents may not be changed like the compact disk read only memory. 4) The average access time of a compact disk is slower than that of a hard disk. Digital versatile disks (DVDs) DVDs are also called digital video disks. With these disks, more data can be packed on the disk. DVDs are suitable for recording motion pictures such as video because they offer better sound and picture quality. DVD-ROMs have a storage capacity of 4.7GB Difference between CDs and DVDs 1) DVDs have higher storage capacity than CDs 2) DVDs are cheaper per unit data storage 3) DVDS guarantee higher quality features (sound and video) 4) CDs are cheaper (cost) than DVDs 5) Reading and writing CDs is faster than on DVDs Variations of CDs and DVDs 1) CD-ROM and DVD-ROM 2) CD-R and DVD-R 3) CD-RW and DVD-RW 4) DVD-RAM 5) Photo CD 6) Blu-Ray disks CD-Rs and DVD-Rs These disks are bought blank and data can be added to the disk (once) but not removed when it is on there. These disks are ideal for single burning or recording of data. Uses of CD-Rs and DVD-Rs : 1) CD-Rs are used for recording music play lists 2) DVD-Rs are used for recording video clips 3) Recording data for archival or backup purposes 4) Transfer data from one computer to another. Advantages of CD-Rs and DVD-Rs 1) Impossible to accidentally delete recorded data 2) Cheaper than CD-RWs and hard disks 3) Easy to transfer information from one computer to another. Disadvantages of CD-Rs and DV-Rs 1) Only recordable once so updating records may be impossible. 2) Very slow data transfer rate. 3) If an error occurs during burning, the disk is damaged and is wasted. Both CD-ROMs and CD-Rs are referred to as (WORM) write once read many because they allow the user to record data on them once but read the data as often as necessary. DVD-RAM disks With DVD-RAM disks, writing and reading of data can happen at the same time. DVD-RAM disks can be rewritten over many many times. Uses of DVD-RAM disks 1) Video and data archiving 2) Recording TV programmes Advantages of DVD-RAM disks 1) Can be re-used many times 2) Stored data can be updated 3) Even if burning of files fails, the disk can still be recorded on later and not wasted. Disadvantages of DVD-RAM disks 1) More expensive than CD-Rs and DVD-Rs 2) Possible to accidentally over write data when updating 3) Data transfer to the disks is very slow Photo CDs Photo CDs use a special format to store digital images. Photo CDs are multisession meaning that new images can be added at any time. Other storage devices Online storage Sometimes called an Internet hard drive-is a service on the web that provides storage to computer users for free or for a minimal monthly fee. Advantages 1) Files stored on an Internet hard drive can be accessed from any computer or device that has web access 2) Share large audio, video and graphics files with others on the Internet 3) Work as an offsite backups of data Magneto-optical disk This combines the best features of magnetic and optical disk technologies. Has a high storage capacity of an optical disk but can be written over like a magnetic disk. Characteristics of storage devices 1) Storage capacity 2) Transfer rate 3) Access time 4) Methods of access Transfer rate Transfer rate is the time it takes a drive to transmit data and information from the drive to another device. Access time Access time is the amount of time it takes to locate an item on a storage medium. Access time is the amount of time required to retrieve data from a storage device. METHODS OF ACCESS There are two methods of data access: 1. Direct access or random access 2. Sequential access or serial access Primary storage devices Primary storage is a form of storage that provides temporary storage for information the computer is currently working on. Primary storage devices are devices that temporarily store information that the computer is currently working on. Primary storage devices provide only temporary or volatile storage that is lose all of the contents when the computer power is turned off. Advantages of primary storage devices 1) High access speed 2) Relatively cheap 3) Always available in all working computers, 4) Not required in large quantity of capacity Disadvantages of primary storage devices 1) Temporal 2) Expensive 3) Limited storage area 4) Delicate especially to electronic fields. Primary storage Vs secondary storage --y ts ye Primary storage Secondary storage 1 Data can be processed 1 | Data cannot be processed directly but must be from directly from storage moved into main memory 2 Located within CPU 2_ | Located outside the CPU 3 More expensive 3__| Less expensive 4 Lower capacity 4 | Higher capacity 5 Faster access time 5 | Slow access time 6. | Volatile 6. | Non volatile