01 03 Storage Structure — Transcript

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1. 0:08[Music]
2. 0:20storage structure
3. 0:24so the storage structure of the computer
4. 0:26systems basically are divided into the
5. 0:29main memory and the secondary storage
6. 0:32now the main memory is the only large
7. 0:34storage media that the cpu can directly
8. 0:37access
9. 0:39so characteristics are it should be
10. 0:41random access or it is random access
11. 0:44typically volatile when say volatile
12. 0:47you've got the temporary storage
13. 0:49okay your data is there
14. 0:52unless there is a power
15. 0:54when the power is gone your data is also
16. 0:56gone that is the volatile
17. 0:58okay
18. 0:59now typically random access memory in
19. 1:02the form of dynamic landmarks memory or
20. 1:05dram
21. 1:07the second one is a secondary storage
22. 1:10so extension of the main memory that
23. 1:12provides a large non-volatile storage
24. 1:14capacity
25. 1:16when we say non-volatile that pertains
26. 1:18to permanent storage
27. 1:21your hard disk is a non-volatile storage
28. 1:26so next would be in the secondary
29. 1:28storage
30. 1:29secondary storage is the extension of
31. 1:31the main memory as mentioned earlier
32. 1:33okay and it includes the magnetic disk
33. 1:36so magnetic disk
34. 1:39or hard disk drive
35. 1:41is a rigid metal or glass platters
36. 1:43covered with magnetic recording material
37. 1:47so desk surface is logically divided
38. 1:50into trucks
39. 1:51and each truck are divided into sector
40. 1:55okay
41. 1:56now the disk controller determines the
42. 1:57logical interaction between the device
43. 2:00and the computer so as mentioned earlier
44. 2:03we have here a controller
45. 2:06because hard disk drive is one of the
46. 2:08peripheral and it should have
47. 2:10their own controller called this
48. 2:12controller
49. 2:13okay
50. 2:14so another storage is the nvm or
51. 2:16non-volatile memory devices
52. 2:19which is faster than hard disk and also
53. 2:22a non-volatile
54. 2:23so various technologies
55. 2:25becoming more popular as capacity and
56. 2:28performance increases
57. 2:30while
58. 2:31lowering the
59. 2:34price okay so let's have some notation
60. 2:38review about the storage basically
61. 2:41the basic unit of computer storage is in
62. 2:43appeal
63. 2:44okay
64. 2:46so when you say bit we are talking about
65. 2:49values of zero and one or in binary bit
66. 2:52is actually binary digit
67. 2:54okay
68. 2:56now a group of eight bits
69. 2:58is one byte
70. 3:00so a byte is eight bits and on most
71. 3:03computers it is the smallest convenient
72. 3:06chunk of storage
73. 3:08okay
74. 3:09another term aside from byte is word
75. 3:12okay so which is given computer
76. 3:14architecture's native unit of data
77. 3:17a word is made up of one or more bytes
78. 3:22okay
79. 3:23so you also have kilobyte
80. 3:26and one kilobyte is equals to
81. 3:291024 bytes same thing with megabyte or
82. 3:33mb that's
83. 3:35one zero two four raised to two bytes
84. 3:38you also have the unit of data in
85. 3:40gigabyte
86. 3:41terabyte
87. 3:42petabyte and so on
88. 3:47storage hierarchy
89. 3:49so storage system organized into
90. 3:51hierarchy so this is based on the speed
91. 3:54cost and volatility so for volatility we
92. 3:57have covered earlier volatile and
93. 4:00non-volatile volatile temporary storage
94. 4:03non-volatile pertains to
95. 4:05permanent storage
96. 4:07we also have the term caching
97. 4:10caching is copying the information into
98. 4:12faster storage system
99. 4:14main memory can be viewed as a cache
100. 4:17for secondary storage
101. 4:20okay so when we move
102. 4:22our data
103. 4:24from the secondary storage or from the
104. 4:26hard disk
105. 4:27going to a faster storage
106. 4:29we call that process as caching
107. 4:32okay so also we have mentioned about the
108. 4:35controller or device controller now this
109. 4:38controller is being managed by a device
110. 4:41driver
111. 4:42okay so device driver for each device
112. 4:45controller to manage io
113. 4:47and that communicates directly with an
114. 4:49operating system
115. 4:51so it provides a uniform interface
116. 4:54between the controller and the kernel or
117. 4:56the operating system itself
118. 5:00storage device hierarchy
119. 5:03so this would be the hierarchy of the
120. 5:05storage devices
121. 5:07and let's divide it into two okay
122. 5:10so memory cache and registers
123. 5:13these are classified to be under
124. 5:15volatile storage
125. 5:17for temporary storage
126. 5:19now non-volatile storage includes
127. 5:22the non-volatile memory hard disk drives
128. 5:26all optical disks and magnetic tips
129. 5:30okay
130. 5:31now registers cache and main memory are
131. 5:34classified to be a primary storage
132. 5:37non-volatile memory and hard disk drives
133. 5:40are secondary storage
134. 5:42and optical desks and magnetic tapes
135. 5:46are classified to be tertiary storage
136. 5:49now when we start from the bottom on
137. 5:51magnetic tapes or tertiary storage
138. 5:54as we go upward
139. 5:56okay so the access time is increasing
140. 6:00you've got faster access on the primary
141. 6:02storage
142. 6:04and then secondary storage down to the
143. 6:06tertiary storage
144. 6:08the access time is decreasing
145. 6:10now on the opposite if we look at on the
146. 6:13storage capacity
147. 6:15as we go higher on the hierarchy
148. 6:18okay so the capacity or the storage
149. 6:21capacity is limited
150. 6:24okay
151. 6:25so from magnetic tips having the larger
152. 6:27capacity
153. 6:28going up to the main memory which has a
154. 6:30limited or smaller capacity
155. 6:33okay
156. 6:34so basically for the storage structure
157. 6:37we have the main memory or ram
158. 6:40so program must be loaded into the ram
159. 6:43to run the program
160. 6:44okay so instructions and data fetched
161. 6:47into the ram
162. 6:49or from the ram
163. 6:50going to the registers
164. 6:52so ram is
165. 6:54volatile
166. 6:56and medium sized and speed
167. 6:58okay so other electronic volatile memory
168. 7:02is faster smaller
169. 7:04and more expensive per bill so that
170. 7:06includes of course the registers
171. 7:08and the cpu cache
172. 7:10okay so non-volatile memory here
173. 7:13permanent storage is slower
174. 7:15larger and less expensive per bit
175. 7:18so that includes
176. 7:20electronic disks magnetic disks
177. 7:23what else optical disks and magnetic
178. 7:25tapes
179. 7:30so how a modern computer works
180. 7:33okay so basically the modern computer
181. 7:35are still based on the von neumann
182. 7:37architecture
183. 7:38okay so you've got the cpu
184. 7:42and all the instructions are being
185. 7:44loaded into the memory
186. 7:46so that is from the device okay so from
187. 7:49the
188. 7:50i o devices or peripherals
189. 7:53so information or data will be fetched
190. 7:55and moved into the memory and the cpu
191. 7:58directly communicates
192. 8:00with the ram
193. 8:02okay so there is a data movement between
194. 8:04the cpu and the memory
195. 8:07so each instruction being executed by
196. 8:09the cpu
197. 8:10is from and to the memory
198. 8:14okay so the cpu initiates
199. 8:17i o requests okay data
200. 8:20and interruption
201. 8:22and it will be loaded into the memory
202. 8:25so basically when we execute program we
203. 8:28fetched it from the hard disk load it
204. 8:31into the ram and then the cpu will get
205. 8:33it from the ram
206. 8:35okay so load it into the
207. 8:37cache and then execute
208. 8:40all right
209. 8:43now we have the next term which is dma
210. 8:47or the direct memory access so we've got
211. 8:50dma here okay so from the device your
212. 8:52data is loaded into the faster access
213. 8:55memory that's dma or direct memory
214. 8:57access
215. 8:58so used for high speed io device able to
216. 9:02transmit information
217. 9:04at close to memory speeds
218. 9:06so device controller transfers blocks of
219. 9:09data
220. 9:10from buffer storage directly to the main
221. 9:12memory without the cpu intervention
222. 9:15so going back from the
223. 9:18diagram here okay
224. 9:20so if you will observe
225. 9:22the cpu is not part of the data movement
226. 9:26okay
227. 9:27so the cpu is not aware
228. 9:30about the data movement from the device
229. 9:32going to the memory
230. 9:34okay so only one interrupt is generated
231. 9:38per block
232. 9:39rather than
233. 9:40one
234. 9:41or the one interrupt per byte
235. 9:53[Music]
236. 10:01you