CS152 Computer Architecture and Engineering Lecture 24 I O Systems II May 5 1999 John Kubiatowicz http cs berkeley edu kubitron lecture slides http www inst eecs berkeley edu cs152 5 5 99 UCB Spring 1999 CS152 Kubiatowicz The Big Picture Where are We Now Today s Topic I O Systems Network Bus Processor Processor Input Input Control Control Memory Datapath 5 5 99 Memory Output Output UCB Spring 1999 Datapath CS152 Kubiatowicz Outline of Today s Lecture Historical discussion of Disks A More queueing theory Interfacing between processor and I O devices RAID disk arrays Summary 5 5 99 UCB Spring 1999 CS152 Kubiatowicz Review I O System Design Issues Performance Expandability Resilience in the face of failure Processor interrupts Cache Memory I O Bus Main Memory I O Controller Disk 5 5 99 Disk I O Controller I O Controller Graphics Network UCB Spring 1999 CS152 Kubiatowicz Technology Trends Disk Capacity now doubles every 18 months before 1990 every 36 months Today Processing Power Doubles Every 18 months Today Memory Size Doubles Every 18 months 4X 3yr The TheI O I O GAP GAP Today Disk Capacity Doubles Every 18 months Disk Positioning Rate Seek Rotate Doubles Every Ten Years 5 5 99 UCB Spring 1999 CS152 Kubiatowicz Storage Technology Drivers Driven by the prevailing computing paradigm 1950s migration from batch to on line processing 1990s migration to ubiquitous computing computers in phones books cars video cameras nationwide fiber optical network with wireless tails Effects on storage industry Embedded storage smaller cheaper more reliable lower power Data utilities high capacity hierarchically managed storage 5 5 99 UCB Spring 1999 CS152 Kubiatowicz Historical Perspective 1956 IBM Ramac early 1970s Winchester Developed for mainframe computers proprietary interfaces Steady shrink in form factor 27 in to 14 in 1970s developments 5 25 inch floppy disk formfactor microcode into mainframe early emergence of industry standard disk interfaces ST506 SASI SMD ESDI Early 1980s PCs and first generation workstations Mid 1980s Client server computing Centralized storage on file server accelerates disk downsizing 8 inch to 5 25 inch Mass market disk drives become a reality industry standards SCSI IPI IDE 5 25 inch drives for standalone PCs End of proprietary interfaces 5 5 99 UCB Spring 1999 CS152 Kubiatowicz Disk History Data density Mbit sq in Capacity of Unit Shown Megabytes 1973 1 7 Mbit sq in 140 MBytes 1979 7 7 Mbit sq in 2 300 MBytes source New York Times 2 23 98 page C3 Makers of disk drives crowd even mroe data into even smaller spaces 5 5 99 UCB Spring 1999 CS152 Kubiatowicz Historical Perspective Late 1980s Early 1990s Laptops notebooks palmtops 3 5 inch 2 5 inch 1 8 inch formfactors Formfactor plus capacity drives market not so much performance Recently Bandwidth improving at 40 year Challenged by DRAM flash RAM in PCMCIA cards still expensive Intel promises but doesn t deliver unattractive MBytes per cubic inch Optical disk fails on performance e g NEXT but finds niche CD ROM 5 5 99 UCB Spring 1999 CS152 Kubiatowicz Disk History 1989 63 Mbit sq in 60 000 MBytes 1997 1450 Mbit sq in 2300 MBytes 1997 3090 Mbit sq in 8100 MBytes source New York Times 2 23 98 page C3 Makers of disk drives crowd even more data into even smaller spaces 5 5 99 UCB Spring 1999 CS152 Kubiatowicz MBits per square inch DRAM as of Disk over time 9 v 22 Mb si 40 35 30 25 20 15 470 v 3000 Mb si 10 5 0 2 v 1 7 Mb si 0 1974 1980 1986 1992 1998 source New York Times 2 23 98 page C3 Makers of disk drives crowd even more data into even smaller spaces 5 5 99 UCB Spring 1999 CS152 Kubiatowicz Nano layered Disk Heads Special sensitivity of Disk head comes from Giant Magneto Resistive effect or GMR IBM is leader in this technology Same technology as TMJ RAM breakthrough we described in earlier class Coil for writing 5 5 99 UCB Spring 1999 CS152 Kubiatowicz Review Disk Device Terminology Disk Latency Queueing Time Controller time Seek Time Rotation Time Xfer Time Order of magnitude times for 4K byte transfers Average Seek 8 ms or less Rotate 4 2 ms 7200 rpm Xfer 1 ms 7200 rpm 5 5 99 UCB Spring 1999 CS152 Kubiatowicz Review Disk Time Example Disk Parameters Transfer size is 8K bytes Advertised average seek is 12 ms Disk spins at 7200 RPM Transfer rate is 4 MB sec Controller overhead is 2 ms Assume that disk is idle so no queuing delay What is Average Disk Access Time for a Sector Ave seek ave rot delay transfer time controller overhead 12 ms 0 5 7200 RPM 60 8 KB 4 MB s 2 ms 12 4 15 2 2 20 ms Advertised seek time assumes no locality typically 1 4 to 1 3 advertised seek time 20 ms 12 ms 5 5 99 UCB Spring 1999 CS152 Kubiatowicz Review Simple Producer Server Model Queue Producer Server Throughput The number of tasks completed by the server in unit time In order to get the highest possible throughput The server should never be idle The queue should never be empty Response time Begins when a task is placed in the queue Ends when it is completed by the server In order to minimize the response time 5 5 99 The queue should be empty The server will be idle UCB Spring 1999 CS152 Kubiatowicz Review Disk I O Performance 300 Metrics Response Time Throughput Response Time ms 200 100 0 100 0 Throughput total BW Queue Proc IOC Device Response time Queue Device Service time 5 5 99 UCB Spring 1999 CS152 Kubiatowicz Response Time vs Productivity Interactive environments Each interaction or transaction has 3 parts Entry Time time for user to enter command System Response Time time between user entry system replies Think Time Time from response until user begins next command 1st transaction 2nd transaction What happens to transaction time as shrink system response time from 1 0 sec to 0 3 sec With Keyboard 4 0 sec entry 9 4 sec think time With Graphics 0 25 sec entry 1 6 sec think time 5 5 99 UCB Spring 1999 CS152 Kubiatowicz Response Time Productivity conventional 0 3s conventional 1 0s graphics 0 3s entry graphics 1 0s 0 00 5 00 resp 10 00 think 15 00 Time 0 7sec off response saves 4 9 sec 34 and 2 0 sec 70 total time per transaction greater productivity Another study everyone gets more done with faster response but novice with fast response expert with slow 5 5 99 UCB Spring 1999 CS152 Kubiatowicz Administrivi a Pending schedule Monday 5 10 Last class wrap up evaluations etc Tuesday 5 11 Oral reports 10 12am and 2 4pmin 306 Soda Signup sheet is on my office door After oral reports at 5pm we will all meet in lab to run final mystery program
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