Lecture 1: Different Types of Storage Media PDF

Different types of storage media Chapter 2 Lecture 1 1 Information Communication Technology Magnetic Storage Media 2 Information Communication Technology Hard Disk Drives (HDD) Data is stored in a digital format on the magnetic surf...

Different types of storage media Chapter 2 Lecture 1 1 Information Communication Technology Magnetic Storage Media 2 Information Communication Technology Hard Disk Drives (HDD) Data is stored in a digital format on the magnetic surfaces of the hard disks (also known as platters). Number of platter in hard disk may depends on capacity of it. Data can be accessed through the read/write head. Read/write heads contain a tiny magnet which allows the data on the platter to be read. Platter can rotate up to 10000rpm (10000 rotation per minute) 3 Information Communication Technology How does HDD works? Actuators are used to control the read/write heads. Tiny magnets in the read/write heads allows the read/write operations on the disk. Data is stored in circular tracks and each track is broken up into sectors. A map of sector is stored on the HDD and is known as file allocation table (FAT). When computer wants to store new files, HDD looks at FAT to know which sector is free and move the read/write head to the free sector to store data. When computer wants to read existing files, HDD looks at FAT to know where the data is stored and move the read/write head to specific sector and track to read data. 4 Information Communication Technology HDD (Tracks and Sectors) 5 Information Communication Technology Uses of HDD To store the operating system, systems software and working data/files. Storing applications software. 6 Information Communication Technology Advantages HDDs have large memory capacities. They have fast data transfer rate and data access time. 7 Information Communication Technology Disadvantages They can be easily damaged if correct procedure on computer has not been performed. Having many moving parts can affect their overall reliability. They can be quite noisy at times. Have latency issues as platter have to be spinning for read/write operations. 8 Information Communication Technology Optical Media Storages 9 Information Communication Technology CD/DVD optical drives Make use of optical properties of laser to read/write data on the surface of the disk. Uses red laser. They use a thin layer of metal alloy or light sensitive dye coating to store the data. Can be described in 3 types: R: can only write once. RW: can be read and written from many times. ROM: can only be read. 10 Information Communication Technology CD-R and DVD-R Uses: Home recordings of music (CD-R) and films (DVD-R). Used to store data to be kept for later use or to be transferred to another computer. Advantages: Cheaper medium than RW disks. Once burned (and finalised) they behave like a ROM. Disadvantages: Can only be recorded once; if an error occurs then the disk has to be thrown away. Not all CD/DVD players can read CD-R/DVD-R. 11 Information Communication Technology CD-RW and DVD-RW Uses: Can be used as a backup device for files and data. Used in CCTV systems Advantages: Can be written over many times Can use different file formats each time it is used. Not as wasteful as R format because the files/data can be added at a later stage. Disadvantages: More expensive than R format. Possible to accidentally overwrite data. 12 Information Communication Technology CD-ROM and DVD-ROM Uses: CD ROM is used to store music files and to store software and computer games. DVD-ROM has much larger storage and is used to store films. Used in applications where there is a real need to prevent the deletion or overwriting of important data. Advantages: They are less expensive than hard disk drive. Disadvantages: The data transfer rate/data access time is slower than for hard disks. 13 Information Communication Technology Blu-ray discs Differences between Blu-ray and DVDs: Make use of blue laser rather than red unlike CDs and DVDs. Blu-ray can store up to five times more data than a normal DVD. Blu-ray comes with secure encryption system. The data transfer rate for a DVD is 10 Mbps and for a Blu-ray disc it is 36 Mbps. Uses: Storing and playing back movies Can be used for storing backup data 14 Information Communication Technology Advantages of Blu-ray discs Very large storage capacity, therefore ideal for storing high-definition movies. Very fast data transfer rate. Blu-ray discs automatically come with a secure encryption system. 15 Information Communication Technology Disadvantages of Blu-ray discs Relatively expensive. Encryption problems when used to store video. 16 Information Communication Technology Solid State Media 17 Information Communication Technology Solid State technology Solid state technology have started to take over hard disks. It removes the latency issue in HDD as data is retrieved at the same rate. Solid state technology stores data by controlling the movement of electrons within NAND chips to produce non-volatile rewritable memory. It stores data as 0s and 1s inside of tiny transistors. Devices that use solid state technology are often referred to as flash memories or flash drives. 18 Information Communication Technology Solid State Drives Solid state drives can be used in the same way as HDD (storing operating system and application software) Integration of solid state drives in laptops have allowed them to become thinner and much lighter. They were first known through the development of smartphones and tablets and without solid state technology these devices simply would not exist. 19 Information Communication Technology Advantages They are more reliable as they have no moving parts. They are considerably lighter than HDD. They do not require to ‘get up to speed’ before they work properly. They are much faster than HDD. 20 Information Communication Technology Disadvantages They have shorter life span compared to HDD. They are more expensive than HDD. 21 Information Communication Technology Pen Drives / Memory Sticks Small portable devices that make use of solid state technology. Can be connected to computer via USB ports. Uses: Transporting files between computers or using as a backing store. Used as a security device to prevent software piracy (known as a dongle). 22 Information Communication Technology Advantages Very compact and portable media Very robust. Does not need additional software to work on most computers. They are not affected by magnetic fields. 23 Information Communication Technology Disadvantages Cannot write protect the data/files by making it ‘read-only’. Easy to lose (due to the small physical size) The user needs to be very careful when removing a memory stick from a computer – incorrect removal will corrupt data on the memory stick. 24 Information Communication Technology Memory Cards Memory cards make use of solid state technology. Can be inserted into a device which can carry out read/write operations on the card. Comes in various size and format. Common formats: SD Cards (secure digital card): commonly used in portable devices such as smart phones, tablets and video camera. XD Cards (extreme digital card): designed for and used in digital camera. CFast Cards (compact fast card): mainly used as removable memory for high-end digital photo and video camera. 25 Information Communication Technology Uses of memory cards Storing photos on digital cameras. Used as mobile phone memory cards. Used in MP3 players to store music files. 26 Information Communication Technology Advantages Very compact – can be easily removed and used in another device or for transferring photos directly to a computer or printer Because they are solid-state memories (and have no moving parts) they are very durable. They can hold large amounts of data. 27 Information Communication Technology Disadvantages Expensive per gigabyte of memory when compared to hard disk drives. Have a lower storage capacity than hard disks. Memory cards are smallest storage device available thus can easily be lost, stolen or damaged. Not all computers come with memory card readers built in; users will often be required to purchase a card reader or USB converter to view the data on a memory card. 28 Information Communication Technology