Notes02 - Outline CS 245: Database System Principles Notes...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
CS 245 Notes 2 1 CS 245: Database System Principles Notes 02: Hardware Steven Whang CS 245 Notes 2 2 Outline • Hardware: Disks • Access Times • Example - Megatron 747 • Optimizations • Other Topics: Storage costs Using secondary storage Disk failures CS 245 Notes 2 3 Hardware DBMS Data Storage CS 245 Notes 2 4 P M C Typical Computer Secondary Storage ... ... CS 245 Notes 2 5 Processor Fast, slow, reduced instruction set, with cache, pipelined… Speed: 100 ! 500 ! 1000 MIPS Memory Fast, slow, non-volatile, read-only,… Access time: 10 -6 ! 10 -9 sec. 1 μ s ! 1 ns CS 245 Notes 2 6 Secondary storage Many flavors: - Disk: Floppy (hard, soft) Removable Packs Winchester Ram disks Optical, CD-ROM… Arrays - Tape Reel, cartridge Robots
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
CS 245 Notes 2 7 Focus on : “Typical Disk” Terms: Platter, Head, Actuator Cylinder, Track Sector (physical), Block (logical), Gap CS 245 Notes 2 8 Top View CS 245 Notes 2 9 Typical Numbers Diameter: 1 inch ! 15 inches Cylinders: 100 ! 2000 Surfaces: 1 (CDs) ! (Tracks/cyl) 2 (floppies) ! 30 Sector Size: 512B ! 50K Capacity: 360 KB (old floppy) ! 2 TB CS 245 Notes 2 10 Disk Access Time block x in memory ? I want block X CS 245 Notes 2 11 Time = Seek Time + Rotational Delay + Transfer Time + Other CS 245 Notes 2 12 Seek Time 3 or 5x x 1 N Cylinders Traveled Time
Background image of page 2
CS 245 Notes 2 13 Average Random Seek Time " " SEEKTIME (i ! j) S = N(N-1) N N i=1 j=1 j # i “Typical” S: 10 ms ! 40 ms CS 245 Notes 2 14 Rotational Delay Head Here Block I Want CS 245 Notes 2 15 Average Rotational Delay R = 1/2 revolution “typical” R = 8.33 ms (3600 RPM) CS 245 Notes 2 16 Transfer Rate: t • “typical” t: 1 ! 3 MB/second • transfer time: block size t CS 245 Notes 2 17 Other Delays • CPU time to issue I/O • Contention for controller • Contention for bus, memory “Typical” Value: 0 CS 245 Notes 2 18 • So far: Random Block Access • What about: Reading “Next” block?
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
CS 245 Notes 2 19 If we do things right (e.g., Double Buffer, Stagger Blocks…) Time to get = Block Size + Negligible block t - skip gap - switch track - once in a while, next cylinder CS 245 Notes 2 20 Rule of Random I/O: Expensive Thumb
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

This document was uploaded on 03/08/2011.

Page1 / 11

Notes02 - Outline CS 245: Database System Principles Notes...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online