Storage devices
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Storage Devices
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Storage devices
- 1. Sunawar Khan STORAGE DEVICES Sunawar Khan MSCS IIUI
- 2. Sunawar Khan Stored-Program Concept The von Neumann architecture
- 3. Sunawar Khan Memory ■ Memory is a collection of cells, each with a unique physical address
- 4. Sunawar Khan MemoryHierarchy Slow and inexpensive Increasing performance and increasing cost
- 5. Sunawar Khan Storage Devices ■ Storage device stores information to be recalled and used at a later time ■ Storage device consists of: ■Storage medium ■Storage device ■ Three major technology types for information storage: ■Magnetic ■Optical or laser ■Flash memory SimNet Concepts Support CD: “Storage Concepts”
- 6. Sunawar Khan Storage MediumTerms – Bit – Byte – Kilobyte (KB) – Megabytes (MB) – Gigabytes (GB) – Terabytes (TB) – Petabyte (PB) – Exabyte (EB) – Zettabyte – Yottabyte Smallest Unit of Memory = 8 bits ≈ 1024 Bytes ≈ 1024 K- Bytes ≈ 1024 M-Bytes ≈ 1024 G-Bytes ≈ 1024T-Bytes ≈ 1024 P-Bytes ≈ 1024 E-Bytes ≈ 1024 Z-Bytes
- 7. Sunawar Khan Bits and bytes ■ A computer only understands the numbers 0 or 1, or whether a switch is on or off. ■ We call those 1s and 0s ‘bits’ – binary digits ■ A byte (made up of 8 bits) is enough computer memory to store a single character of data (e.g. the letter F). ■ The computer uses a code to understand what each bit pattern means. ■ Using the ASCII code, for instance, the letter F is 70 and has a bit pattern of 01000110.
- 8. Sunawar Khan Magnetic and Optical Storage Storage Media Magnetic Storage Media Sealed Inside Drive Internal Hard Drive External hard Drive Removeable Storage Media Floppy Disk Zip Disk Optical Storage Media CD CD-ROM CD RW CD R DVD DVD ROM DVD RW Blue Ray Disk
- 9. Sunawar Khan Levels of Storage Hierarchy Levels Online Storage Near-Online Storage Offline Storgae
- 10. Sunawar Khan Magnetic Storage Media ■ Magnetic storage devices can be either internal or external • Internal magnetic hard disks are fixed inside the system unit • External magnetic hard disks are portable
- 11. Sunawar Khan Magnetic Disks ■ A read/write head travels across a spinning magnetic disk, retrieving or recording data The organization of a magnetic disk
- 12. Sunawar Khan Internal Magnetic Hard Disk ■ Internal hard disk is a magnetic storage device with • One or more thin platters that store information sealed inside the disk drive. • Read/write heads access the information on surface • Heads read information while copying it from disk to RAM • Heads write information when copying it from RAM to disk ■ Long term storage system and application software ■ Operating system and application software are copied from the hard disk to memory ■ Capacity measured in gigabytes
- 13. Sunawar Khan Hard Disk ■ The hard drive is the main and usually largest data storage device in computer. ■ It can store anywhere from 160 GB to 2TB. ■ 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.
- 14. Sunawar Khan Disk Storage Head Assembly All heads move together Platter Sector Top and bottom Surfaces Head SpindleTrack Shaft Arm
- 15. Sunawar Khan Disk Storage Cylinder X: Track X from all 12 surfaces (2 per platter) Each circle represents two tracks: one for top surface and one for bottom surface
- 16. Sunawar Khan Disk Storage (a) Normal (Non zoned) recording (b) Zoned recording
- 17. Sunawar Khan External Magnetic Hard Disk ■ External hard disks are magnetic storage media which are portable storage units that you can connect to your computer as necessary • Great for backup storage devices • Ability to transport your hard disk from one computer to another
- 19. Sunawar Khan MagneticTape ■ The first truly mass auxiliary storage device was the magnetic tape drive A magnetic tape
- 20. Sunawar Khan Types of backing storage The medium is what the data is actually stored on. Examples of media include floppy disks, CD-ROMs and zip disks. Floppy disks hold about 1.44 MB of data. Zip disks store up to 750 MB of data. CDs hold around 700 MB of data.
- 21. Sunawar Khan Removable Magnetic Storage: Floppy Disk ■ Floppy Mylar disk – Housed inside a hard plastic casing – Thin, flexible plastic disk ■ 3.5 inch floppy disks – also called floppies, diskettes, floppy disks – Holds about 1.44 megabytes of information ■ High-capacity disks – Zip® disk p. 5.144 Fig. 5.15
- 23. Sunawar Khan Removable Magnetic Storage: Zip Disk ■ High capacity plastic platter disk – Called removable hard disks – Provide a higher storage capacity than Mylar disks ■ Example - Zip® disk with capacity of 100MB, 250MB, and 750MB
- 24. Sunawar Khan Optical Storage Media ■ Read-Only CD-ROM DVD-ROM ■ One-TimeWritable CD-R DVD-R DVD+R ■ Fully Read-and- Write CD-RW DVD-RW or DVD+RW or DVD-RAM
- 25. Sunawar Khan Optical Storage ■ CDs ■ DVDs ■ Both are optical storage and have three formats: – Read-only – Write-once – Read-and-write
- 27. Sunawar Khan Flash Memory Cards ■ Flash memory cards have high-capacity storage laminated inside a small piece of plastic ■ Flash flash memory cards do not need a drive with moving parts to operate
- 28. Sunawar Khan Zip Disk Drive
- 29. Sunawar Khan USB Flash Drive
- 31. Sunawar Khan Data is stored using binary code (0 and 1). Computer memory is measured in kilobytes. Read Only Memory (ROM) is non-volatile because it cannot be changed. Random Access Memory (RAM) is volatile because it only works when the computer is switched on. There are three types of storage device: those that use magnetic media, others that use optical media, and those that use flash memory. Different types of media have different storage capacities. Storage devices can also be divided into those that are fixed and those that are removable. Summary