Here are my slides from lecture, along with my notes about each slide.

Transcription

1 Chapter 3: Storage Here are my slides from lecture, along with my notes about each slide. NOTE: You are expected to attend all class meetings. Please be in the room when class begins and be ready to participate actively. These lecture handouts are NOT a substitute to class attendance; they are to complement your class notes and memories. 1

2 CIS 141 Unit 1 covers three chapters in your textbook: Chapter 2 focuses on Processing (e.g., the things on the motherboard, including the CPU, GPU, RAM, busses, expansion slots, and ports) Chapter 3 focuses on Storage (non-volatile, long-term storage of data and information) Chapter 4 focuses on Input and Output Hardware (for getting data INTO the system and getting information OUT of the system) Together these represent Computer Hardware which is the physical components of a computer. Hardware is all the stuff you can touch and feel. 2

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4 In chapter 2 we discussed the CPU and RAM memory, both of which are volatile which means they need power (electricity) to maintain their data. Storage is nonvolatile and therefore a long term way to store data. Storage does not lose its data when you turn the power off. 4

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6 Traditional hard drives contain metal platters with a coating of magnetic material that can be changed and read by a read-write head at the end of a mechanical arm. (The read-write head is circled in red in the figure above.) The metal platters spin VERY RAPIDLY, rotating over 8000 times per minute. 6

7 The read-write head gets VERY CLOSE to the platter, but does not touch. The distance is closer than a speck of dust or a particle of smoke. (For this reason, hard drives are sealed inside air-tight containers and cannot be opened without damaging the hard drive.) If the hard drive is shaken while the platters are spinning, the read/write head might accidentally vibrate and touch the spinning platter, which will destroy the read/write head (called a head crash). If there is a head crash, the data on the drive is basically lost. Some data recovery businesses might be able to recover some of the data, but it will cost multiple hundreds of dollars just for them to try with no assurance of any data actually being recovered. 7

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9 Moore s law is relatively well known. A lesser known observation about advancements with computing technology is Kryder s law that storage doubles about every year. That is faster doubling than Moore s Law. (Kryder was talking specifically magnetic storage, but all storage types seem to be doubling at significant rates.) 9

10 In 1980, magnetic storage cost about $112,000 per Gigabyte (adjusted to current dollars). Today, magnetic storage costs about 5 cents per Gigabyte (or about $53 per Terabyte) 10

11 Another example (significant decrease in size and price, and significant increase in capacity) 11

12 Another example (128 MB vs 128 GB) on the same size storage device 12

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14 Magnetic Storage There are three common types of storage: magnetic, solid state, and optical. The traditional hard drive uses magnetic material on the spinning platters and a magnetic read/write head that floats on a layer of air very close to the platters (smaller than the width of a human hair) without touching the platters. If the read/write head touches the spinning platters, you will have a disk failure and the hard drive will be unusable. 14

15 Solid State (or Flash) Storage There are three common types of storage: magnetic, solid state, and optical. Flash storage has no moving parts, and is therefore solid state. Flash storage is chip-based and represents data using electrons. Flash storage is what you see in USB thumb drives, in the memory cards for smart phones and cameras. There are even smart cards that use flash storage rather than magnetic strips to store user information. 15

16 Optical Storage There are three common types of storage: magnetic, solid state, and optical. Optical storage used lasers to read and write data. Optical storage devices are CDs, DVDs, and BluRay. NOTE: When referring to optical storage, the term disc with a c is uses (The term disk with a k is used for for magnetic disks.) 16

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18 Remote storage refers to using a storage device that is not connected directly to the user s computer. NAS refers to Network Access Storage Cloud storage is storage service accessed via the Internet 18

19 End of Lecture 19