Lecture_13 - Lecture 13 Storage Network and Other Peripherals Oth 1 I/O Systems Processor interrupts Cache Processor I/O Communication Memory I/O

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Lecture 13 Storage, Network and Other Peripherals 1
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I/O Systems Processor interrupts Cache Processor & I/O Communication Memory - I/O Bus Main emory I/O ontroller I/O ontroller I/O ontroller Memory Controller Disk Disk Controller Controller Graphics Network 2
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I O /O I/O System Evaluation Metric Dependability xpandability Expandability Cost Performance I O Device Characteristics /O e ce C a acte st cs Behavior » Input, output or storage Partner Data rate Device Behavior Partner Data Rate (KB/sec) () Keyboard Input Human 0.01 Mouse Input Human 0.02 Floppy disk Storage Machine 50.00 Laser Printer Output Human 100.00 Optical Disk Storage Machine 500.00 Magnetic Disk Storage Machine 5,000.00 3 Network-LAN Input or Output Machine 20 1,000.00 Graphics Display Output Human 30,000.00
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I/O System Performance I/O System performance depends on many aspects of the system ( limited by weakest link in the chain ): The CPU The memory system: » Internal and external caches » Main Memory The underlying interconnection (buses) he I/O controller The I/O controller The I/O device The speed of the I/O software (Operating System) The efficiency of the software s use of the I/O devices Two common performance metrics: hroughput: Throughput: » How much data can we move through the system in a certain time? ( data rate ) ow many I/O operations can we do per unit of time? ( O rate 4 » How many I/O operations can we do per unit of time? ( I/O rate ) Response time: Latency
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Organization of a Hard Magnetic Disk Platters Track Purpose: Sector p Long-term, nonvolatile storage Large, inexpensive, slow level in the storage hierarchy 5
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Devices: Magnetic Disks Sector Track Read/Write data is three-stage process: Seek Time (~20 ms avg, 1M cyc at 50MHz) ove arm over track ylinder » move arm over track rotational latency - » wait for the sector to rotate under head Cylinder Head Platter » Average = (0.5)/3600RPM = 8.3ms Transfer rate bout a sector per ms (1- 0 MB/s) » About a sector per ms (1 10 MB/s) Controller time The overhead of controller imposes in performing n I/O access an I/O access Disk Latency = Seek Time + Rotation Time + Xfer Time + Controller time 6
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Disk Time Example Disk Parameters: 512-byte sector Advertised average seek time is 6 ms Transfer rate is 50 MB/sec Disk spins at 10,000 RPM. Controller overhead is 0.2ms Assume that the disk is idle so there is no waiting time What is the average time to read/write a sector? ve seek time + ave rot time + xfer time + control overhead Ave seek time + ave rot time + xfer time + control overhead 6 + 0.5 / 10,000RPM + 0.5KB / (50 MB/sec) + 0.2 = 9.2 7
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Reliability, Availability and Dependability Dependability omputer System ependability the uality of Computer System dependability is the quality of delivered service such that reliance can justifiably be placed on this service. The service delivered by a system is its observed actual behavior as perceived by other systems interacting with the system s users. Each
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This note was uploaded on 09/24/2009 for the course CSIE CA2009 taught by Professor Yang during the Spring '09 term at National Taiwan University.

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Lecture_13 - Lecture 13 Storage Network and Other Peripherals Oth 1 I/O Systems Processor interrupts Cache Processor I/O Communication Memory I/O

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