Dept. of Computer Science & Engineering, CUHK Performance and Effectiveness Analysis of Checkpointing in Mobile Environments Chen Xinyu 2003-01-22.

Dept. of Computer Science & Engineering, CUHK

Performance and Effectiveness Analysis of Checkpointing in

Mobile Environments

Chen Xinyu

2003-01-22

Introduction

Mobile Environment – Wireless CORBA

Performance and Effectiveness Analysis of Checkpointing

Conclusions and Future Work

Outline

Introduction

Mobile Computing Permanent failures

Physical damage

Transient failures Mobile hosts Wireless links Environmental conditions

Checkpointing and Rollback Recovery

Checkpoint the saved program’s states during failure-free

execution

Repair brings the failed device back to normal operation

Rollback reloads the program’s states saved at the most

recent checkpoint

Recovery the reprocessing of the program, starting from the

most recent checkpoint, applying the logged messages and until the point just before the failure

Wireless CORBA Architecture

Visited Domain

Home Domain

Terminal Domain

Access Bridge

Access Bridge

Access Bridge

Access Bridge

Static Host

Static Host

Terminal Bridge

GIOP

Tunnel

ab1

ab2

mh1

GTP Messages

Wireless CORBA Architecture

Visited Domain

ab1

ab2

Access Bridge

Access Bridge

Static Host

Static Host

Home Domain

Home Location

Agent

Terminal Domain Terminal

Bridge

GIOP

Tunnelmh1

mh1

Terminal Domain Terminal

Bridge

GIOP

Tunnel

GIOP

Tunnel

mh1

Terminal Domain Terminal

BridgeGIOP Tunnel

mh1

Terminal Domain Terminal

Bridge

Access Bridge

Access Bridge

Introduction

Mobile Environment – Wireless CORBA

Performance and Effectiveness Analysis of Checkpointing

Conclusions and Future Work

Outline

Program’s Termination Condition

A program is successfully terminated if it receives N computational messages continuously

Assumptions

Failure occurrence, message arrival and handoff event

homogeneous Poisson process with parameter , and respectively

Failures do not occur when the program is in the repair or rollback process

A failure is detected as soon as it occurs

Execution without Checkpointing

RY0

X0

R

F1

H1Z0

0 t

Fj

Hk

mj(1) mj(N)m1(n1)m0(N)

X(N)

Repair Handoff

H H

Conditional Execution Time without checkpointing

LST without checkpointing

LST and Expectation of Program Execution Time

Bounded Situations

Without handoff

Without handoff and failure

Execution with Equi-number Checkpointing

Ci

R+CYi(0)

Xi(0)

R+C

Fi(1)

Hi(1)Z i(0)

0 t

Fi(j)

Hi(k)

mij(1) mij(a)mi1(ni1)mi0(a)

Xi(N,a)

Repair + Rollback Handoff

Ci-1

Checkpointing

H H CC

Conditional Execution Time & LST with Checkpointing

LST and Expectation of Program Execution Time

Average Effectiveness

Effective interval: a program produces useful work towards its completion

Wasted interval: Repair and rollback Handoff Checkpoint creation Wasted Computation

Average Effectiveness: how much of the time an MH is in effective interval during an execution

Optimal Checkpointing Interval

Beneficial Condition

Equi-number Checkpointing

Equi-number checkpointing with respect to message number Message number in each checkpointing interval is

not changed

Equi-number checkpointing with respect to checkpoint number Checkpoint number is not changed

Equi-number Checkpointing with respect to Checkpoint Number

Equi-number Checkpointing with respect to Message Number

Comparison Between Checkpointing and Without Checkpointing

Average Effectiveness vs. Message Arrival Rate and Handoff Rate

Conclusions

Introduce an equi-number checkpoiting strategy

Derive LST and expectation of program execution time

Derive average effectiveness Derive optimal checkpointing

interval Identify the beneficial condition

Future Work

Analytical model Message queuing effect during repair and

recovery General event distributions

Fault tolerance in ad hoc network Without infrastructure support Self-organizing and adaptive

Thank You