Fundamentals of Computing Chapter 6
- 1. 1 CSCA0201 FUNDAMENTALS OF COMPUTING Chapter 5 Storage Devices CSCA0201 FUNDAMENTALS OF COMPUTING Chapter 6 Storage Devices
- 2. 2 Chapter 6 Storage Devices Storage Devices • A storage device is any computer hardware that stores data. • Provides one of the core functions of the modern computer.
- 3. 3 Chapter 6 Storage Devices Types of Storage • Primary Storage • Secondary Storage • Off-line Storage • Cloud Storage
- 4. 4 Chapter 6 Storage Devices Primary Storage • Primary storage, also known as main storage or memory, is the area in a computer in which data is stored for quick access by the computer's processor. • It is directly or indirectly connected to the CPU via a memory bus. • The CPU continuously reads instructions stored there and executes them as required. • Examples: – Random Access Memory (RAM) – Cache
- 5. 5 Chapter 6 Storage Devices Primary Storage Random Access Memory (RAM) • It is called Random Access Memory because any of the data in RAM can be accessed just as fast as any of the other data. • There are two types of RAM: – SRAM (Static Random Access Memory) – DRAM (Dynamic Random Access Memory) • Extended Data Out Dynamic RAM (EDO RAM) • Synchronous Dynamic RAM (SDRAM) • Single Data Rate Synchronous Dynamic RAM (SDR SDRAM) • Double Data Rate Synchronous Dynamic RAM (DDR SDRAM)
- 6. 6 Chapter 6 Storage Devices Primary Storage Static RAM Dynamic RAM • Faster access speed • More expensive • More power consumption • Does not need to be refreshed • Lesser memory capacities • Higher costs of manufacturing • Slower access speed • Less expensive • Less power consumption • needs to be refreshed thousands of times per second • Lower costs of manufacturing • Greater memory capacities.
- 7. 7 Chapter 6 Storage Devices Primary Storage Cache • Cache is a high-speed access area that can be either a reserved section of main memory or a storage device. • Stores frequently used computer programs, applications and data. • Most computers today come with L3 cache or L2 cache, while older computers included only L1 cache.
- 8. 8 Chapter 6 Storage Devices Secondary Storage • It is not directly accessible by the CPU. • Computer usually uses its input/output channels to access secondary storage and transfers the desired data using intermediate area in primary storage. • Example: – Hard Disk – Solid-State Disk
- 9. 9 Chapter 6 Storage Devices Secondary Storage Hard Disk • The hard disk drive is the main, and usually largest, data storage device in a computer. • It can store anywhere from 160 gigabytes to 2 terabytes. • Hard disk speed is the speed at which content can be read and written on a hard disk. • A hard disk unit comes with a set rotation speed varying from 4500 to 7200 rpm. • Disk access time is measured in milliseconds. Internal Hard disk External Hard disk
- 10. 10 Chapter 6 Storage Devices Secondary Storage Solid-State Disk (SSD) • SSD is a drive that uses non-volatile memory as a means of storing and accessing data, much like computer RAM. • Unlike a hard drive, an SSD has no moving parts, which gives it advantages such as accessing stored information faster, noiseless operation, higher reliability, and lower power consumption. • SSDs are also a great solution for netbooks and other applications that don't require a lot of storage.
- 11. 11 Chapter 6 Storage Devices Off-line Storage • Also known as disconnected storage. • Is a computer data storage on a medium or a device that is not under the control of a processing unit. • It must be inserted or connected by a human operator before a computer can access it again.
- 12. 12 Chapter 6 Storage Devices Off-line Storage • Examples: – Floppy Disk – Zip diskette – Optical Disc – USB Flash drive – Memory card
- 13. 13 Chapter 6 Storage Devices Off-line Storage Floppy Disk • A soft magnetic disk. • Floppy disks are portable. • Floppy disks are slower to access than hard disks and have less storage capacity, but they are much less expensive. • Can store data up to 1.44MB. • Two common sizes: 5 ¼” and 3 ½”.
- 14. 14 Chapter 6 Storage Devices Off-line Storage Floppy Disk 5 inch Floppy Disk 3 inch Floppy Disk Floppy Disk Drive
- 15. 15 Chapter 6 Storage Devices Off-line Storage Zip Diskette • Hardware data storage device developed by Iomega that functions like a Standard 1.44" floppy drive. • Capable to hold up to 100 MB or 250 MB of data on new drives. • Now it less popular as users needed larger storage capabilities. Zip Diskette Zip Drive
- 16. 16 Chapter 6 Storage Devices Off-line Storage Optical Disc • Optical disc is any storage media that holds content in digital format and is read using a laser assembly is considered optical media. • The most common types of optical media are – Blu-ray (BD) – Digital Versatile Disc (DVD) – Compact Disc (CD)
- 17. 17 Chapter 6 Storage Devices Off-line Storage Optical Disc CD DVD BD Capacity 700MB 4.7GB – 17GB 50GB Wavelength 780nm 650nm 405nm Read/Write Speed 1200KB/s 10.5MB/s 36MB/s
- 18. 18 Chapter 6 Storage Devices Off-line Storage Optical Disc – Recordable vs. ReWritable • Recordable discs can be written to only once. • They are cheap and work best when recording data that will not change • ReWritable discs can be written to many times, and they function somewhat like a hard disk or floppy. • To store small amounts of data over time, such as a daily backup of a few critical files.
- 19. 19 Chapter 6 Storage Devices Off-line Storage USB Flash Drive • A small, portable flash memory card that plugs into a computer’s USB port and functions as a portable hard drive. • Flash drives are available in sizes such as 8GB to 64GB and are an easy way to transfer and store information.
- 20. 20 Chapter 6 Storage Devices Off-line Storage Memory Card • A memory card is a type of storage device that is used for storing media and data files. • It provides a permanent and non-volatile medium to store data and files from the attached device. • Memory cards are commonly used in small, portable devices, such as cameras and phones. • Memory cards are usually read by connecting the device containing the card to your computer, or by using a USB card reader.
- 21. 21 Chapter 6 Storage Devices Off-line Storage Memory Card Secure Digital card (SD) MiniSD Compact Flash Memory Stick MultiMedia card XD-Picture card Memory card reader
- 22. 22 Chapter 6 Storage Devices Cloud Storage • Cloud storage is defined as "the storage of data online in the cloud, wherein a data is stored in and accessible from multiple distributed and connected resources that comprise a cloud. • Cloud storage can provide the benefits of greater accessibility and reliability; rapid deployment; strong protection for data backup, archival and disaster recovery purposes. • Files stored in the cloud can be accessed at any time from any place so long as you have Internet access.
- 23. 23 Chapter 6 Storage Devices Cloud Storage • Cloud storage provides organizations with off-site (remote) backups of data which reduces costs associated with disaster recovery . • The biggest disadvantage to cloud storage is that users are limited by bandwidth.
- 24. 24 Chapter 6 Storage Devices Characteristics of Storage Device • Volatility • Accessibility • Mutability • Addressability
- 25. 25 Chapter 6 Storage Devices Volatility vs. Non-Volatile Memory Volatile Memory • Requires constant power to maintain the stored information. • The fastest memory technologies. • All contents are erased when the system's power is turned off or interrupted. • It has been more popularly known as temporary memory. • Example: Primary Storage
- 26. 26 Chapter 6 Storage Devices Volatility vs. Non-Volatile Memory Non-Volatile Memory • Will retain the stored information even if it is not constantly supplied with electric power. • Non volatile memory is the device which keeps the data even when the current is off. • It is suitable for long-term storage of information. • Examples: Secondary and Off-line Storage
- 27. 27 Chapter 6 Storage Devices Accessibility • Refers to reading or writing data records • Two types of accessibility: – Random access – Sequential access
- 28. 28 Chapter 6 Storage Devices Accessibility Random Access • Any location in storage can be accessed at any moment in approximately the same amount of time. • Such characteristic is well suited for primary and secondary storage. • Example: RAM, Hard Disk
- 29. 29 Chapter 6 Storage Devices Accessibility Sequential Access • The accessing of pieces of information will be in a serial order, one after the other; therefore the time to access a particular piece of information depends upon which piece of information was last accessed. • Such characteristic is typical of off-line storage. • Example: Magnetic Tape
- 30. 30 Chapter 6 Storage Devices Mutability • Three types of mutability: – Read/write storage or mutable storage – Read only storage – Slow write, fast read storage
- 31. 31 Chapter 6 Storage Devices Mutability Read/Write Storage or Mutable Storage • Allows information to be overwritten at any time. • A computer without some amount of read/write storage for primary storage purposes would be useless for many tasks. • Example: RAM, Hard Disk
- 32. 32 Chapter 6 Storage Devices Mutability Read Only Storage • Retains the information stored at the time of manufacture, and write once storage (WORM) allows the information to be written only once at some point after manufacture. • These are called immutable storage. • Example: CD-R
- 33. 33 Chapter 6 Storage Devices Mutability Slow Write, Fast Read Storage • Read/write storage which allows information to be overwritten multiple times, but with the write operation being much slower than the read operation. • Example: CD-RW
- 34. 34 Chapter 6 Storage Devices Addressability • Three types of addressability – Location-addressable – File addressable – Content-addressable
- 35. 35 Chapter 6 Storage Devices Addressability Location-addressable • Each individually accessible unit of information in storage is selected with its numerical memory address. • Location-addressable storage usually limits to primary storage, accessed internally by computer programs, since location-addressability is very efficient, but burdensome for humans.
- 36. 36 Chapter 6 Storage Devices Addressability File addressable • Information is divided into files of variable length, and a particular file is selected with human-readable directory and file names.
- 37. 37 Chapter 6 Storage Devices Addressability Content-addressable • Each individually accessible unit of information is selected based on the basis of (part of) the contents stored there. • Content-addressable storage can be implemented using software (computer program) or hardware (computer device), with hardware being faster but more expensive option.