chapter 111 chapter 11: hardware (slides by hector garcia-molina, hector/cs245/notes.htm)
TRANSCRIPT
![Page 1: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/1.jpg)
Chapter 11 1
Chapter 11: Hardware
(Slides by Hector Garcia-Molina,http://www-db.stanford.edu/~hector/cs245/
notes.htm)
![Page 2: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/2.jpg)
Chapter 11 2
Outline• Hardware: Disks• Access Times• Optimizations• Other Topics:
– Storage costs– Using secondary storage– Disk failures
![Page 3: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/3.jpg)
Chapter 11 3
The Big Picture:
DBMS
Data Storage
![Page 4: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/4.jpg)
Chapter 11 4
P
M
TypicalComputer
SecondaryStorage
...
![Page 5: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/5.jpg)
Chapter 11 5
ProcessorFast, slow, reduced instruction set,
with cache, pipelined…Speed: 100 500 1000 MIPS
MemoryFast, slow, non-volatile, read-only,…Access time: 10-6 10-9 sec.
1 s 1 ns
![Page 6: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/6.jpg)
Chapter 11 6
Secondary storageMany flavors:
- Disk: Floppy (hard, soft)Removable PacksWinchesterRam disksOptical, CD-ROM…Arrays
- Tape Reel, cartridgeRobots
![Page 7: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/7.jpg)
Chapter 11 7
Focus on: “Typical Disk”
Terms: Platter, Head, Cylinder, TrackSector (physical),Block (logical), Gap
…
![Page 8: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/8.jpg)
Chapter 11 8
Top View
![Page 9: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/9.jpg)
Chapter 11 9
“Typical” NumbersDiameter: 1 inch 15 inchesCylinders: 100 2000Surfaces: 1 (CDs) (Tracks/cyl) 2 (floppies) 30Sector Size:512B 50KCapacity: 360 KB (old floppy)
30 GB (I use)
![Page 10: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/10.jpg)
Chapter 11 10
Disk Access Time
block xin memory
?
I wantblock X
![Page 11: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/11.jpg)
Chapter 11 11
Time = Seek Time +Rotational Delay +Transfer Time +Other
![Page 12: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/12.jpg)
Chapter 11 12
Rotational Delay
Head Here
Block I Want
![Page 13: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/13.jpg)
Chapter 11 13
Average Rotational Delay
R = 1/2 revolution
“typical” R = 8.33 ms (3600 RPM)
![Page 14: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/14.jpg)
Chapter 11 14
Transfer Rate: t
• “typical” t: 1 3 MB/second• transfer time: block size
t
![Page 15: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/15.jpg)
Chapter 11 15
Other Delays
• CPU time to issue I/O• Contention for controller• Contention for bus, memory
“Typical” Value: 0
![Page 16: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/16.jpg)
Chapter 11 16
• So far: Random Block Access• What about: Reading “Next” block?
![Page 17: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/17.jpg)
Chapter 11 17
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
![Page 18: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/18.jpg)
Chapter 11 18
Rule of Random I/O: ExpensiveThumb Sequential I/O: Much less• Ex: 1 KB Block
»Random I/O: 20 ms.»Sequential I/O: 1 ms.
![Page 19: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/19.jpg)
Chapter 11 19
Cost for Writing similar to Reading
…. unless we want to verify! need to add (full) rotation + Block size
t
![Page 20: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/20.jpg)
Chapter 11 20
• To Modify a Block?
To Modify Block:(a) Read Block(b) Modify in Memory(c) Write Block[(d) Verify?]
![Page 21: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/21.jpg)
Chapter 11 21
Block Address:
• Physical Device• Cylinder #• Surface #• Sector
![Page 22: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/22.jpg)
Chapter 11 22
Outline• Hardware: Disks• Access Times• Optimizations• Other Topics
– Storage Costs– Using Secondary Storage– Disk Failures
here
![Page 23: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/23.jpg)
Chapter 11 23
Optimizations (in controller or O.S.)
• Double Buffering• Disk Scheduling Algorithms: sec.
11.5.4– e.g., elevator algorithm
![Page 24: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/24.jpg)
Chapter 11 24
Double Buffering
Problem: Have a File» Sequence of Blocks B1, B2
Have a Program» Process B1» Process B2» Process B3
...
![Page 25: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/25.jpg)
Chapter 11 25
Single Buffer Solution
(1) Read B1 Buffer(2) Process Data in Buffer(3) Read B2 Buffer(4) Process Data in Buffer ...
![Page 26: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/26.jpg)
Chapter 11 26
Say P = time to process/blockR = time to read in 1 blockn = # blocks
Single buffer time = n(P+R)
![Page 27: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/27.jpg)
Chapter 11 27
Double Buffering
Memory:
Disk: A B C D GE F
A B
done
process
AC
process
B
done
![Page 28: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/28.jpg)
Chapter 11 28
Say P R
What is processing time?
P = Processing time/blockR = IO time/blockn = # blocks
• Double buffering time = R + nP
• Single buffering time = n(R+P)
![Page 29: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/29.jpg)
Chapter 11 29
Block Size Selection?
• Big Block Amortize I/O Cost
• Big Block Read in more useless stuff! and takes longer to read
Unfortunately...
![Page 30: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/30.jpg)
Chapter 11 30
Trend
• As memory prices drop, blocks get bigger ...
Trend
![Page 31: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/31.jpg)
Chapter 11 31
Storage Cost
10-9 10-6 10-3 10-0 103
access time (sec)
1015
1013
1011
109
107
105
103
cache
electronicmain
electronicsecondary
magneticopticaldisks
tape
opticaldisks
tape
typi
cal c
apac
ity
(byt
es)
from Gray & Reuter
![Page 32: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/32.jpg)
Chapter 11 32
Storage Cost
10-9 10-6 10-3 10-0 103
access time (sec)
104
102
100
10-2
10-4
cache
electronicmain
electronicsecondary magnetic
opticaldisks
tape
opticaldisks
tape
doll
ars/
MB
from Gray & Reuter
![Page 33: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/33.jpg)
Chapter 11 33
Using secondary storage effectively
• Example: Sorting data on disk• Conclusion:
– I/O costs dominate– Design algorithms to reduce I/O
• Also: How big should blocks be?
![Page 34: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/34.jpg)
Chapter 11 34
Disk Failures (Sec 11.6)
• Partial Total• Intermittent Permanent
![Page 35: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/35.jpg)
Chapter 11 35
Coping with Disk Failures
• Detection– e.g. Checksum
• Correction Redundancy
![Page 36: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/36.jpg)
Chapter 11 36
At what level do we cope?
• Single Disk– e.g., Error Correcting Codes
• Disk Array
Logical Physical
![Page 37: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/37.jpg)
Chapter 11 37
Operating System e.g., Stable Storage
Logical Block Copy A Copy B
![Page 38: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/38.jpg)
Chapter 11 38
Database System
• e.g.,
LogCurrent DB Last week’s DB
![Page 39: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/39.jpg)
Chapter 11 39
Summary
• Secondary storage, mainly disks• I/O times• I/Os should be avoided,
especially random ones…..
Summary
![Page 40: Chapter 111 Chapter 11: Hardware (Slides by Hector Garcia-Molina, hector/cs245/notes.htm)](https://reader030.vdocuments.net/reader030/viewer/2022020716/56649e895503460f94b8e601/html5/thumbnails/40.jpg)
Chapter 11 40
Outline• Hardware: Disks• Access Times• Optimizations• Other Topics
– Storage Costs– Using Secondary Storage– Disk Failures
here