Nonstop computers

資訊科技一指導教授 : 莊裕澤報告者 : 　 黃春照 , 黃錫

煙　 2002/3/28

Definition

Nonstop computer refers to a computer system that runs 24 hours a day, 7 days a week, and 365 days a year.

The computer should remain functional even when one or more of its components fail.

AvailabilityMTBF

A= MTBF + MTTR

Availability Downtime

90% (1-nine) 36.5 days/year

99% (2-nines) 3.65 days/year

99.9% (3-nines) 8.76 hours/year

99.99% (4-nines) 52 minutes/year

99.999% (5-nines) 5 minutes/year

99.9999% (6-nines) 31 seconds/year !

Source:Gartner group

System outage reasons

Source:Gartner group

Who need it ? Aerospace related systems such as computers o

nboard the space shuttle. Online reservation systems such as American Air

lines’ Sabre. Trading systems such as New York Stock Exchan

ge System. Emergency 119 Credit card authorization system

Downtime costs

Industry/Operation Average cost / hour

Brokerage US$5.6M~7.3M

Credit card authorization

US$2.2M~3.1M

Home shopping US$87K~140K

Airline reservation US$67K~112K

Subway ticket sales US$56K~82K

Parcel shipping US$24K~32K

The solution

Preventive Approach

Passive Approach Active Approach

Preventive approach

時間

Failure

Rate

Infant

MortalityUseful Life End of Life

Back

Passive Approach

copy 0: Active

copy 1: Standby

copy 0: Fail

copy 2: Active

copy 0: Diagnostic

copy 1: Active

copy 0: Suspect

copy 1: Active

copy 0: Standby

copy 1: Active

copy 0:faultreported

copy 0failed

copy 0ok

switchover

copy 0replaced

Monitoring methods

Sanity Monitoring Watchdog Monitoring In-service Diagnostics Transient Leaky Bucket Counters

Back

Active Approach

San(Storage area network)