Network Reliability: Fault Tolerance and Related Issues, Slides of Computer Security

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Network Reliability: Fault Tolerance and

Other Issues

Chapter Objectives

• Discuss network reliability issues
  • Fault tolerance, tape backup, UPS etc
• Describe different levels of fault tolerance
  • Levels 1, 2 and 3
  • Examine the relevance of file allocation tables to fault tolerance
• Explain RAID technology

END OF CHAPTER INTRODUCTION

MODULE

An Overview of Network Reliability

Fault Tolerance

• The ability to continue to function when a fault occurs
• Example
  • A server with built-in fault tolerance can continue to operate even when one of its hard disks fails

Focus of Fault Tolerant Features

• Most fault tolerance features are centered on a

server

• Disk storage in the server is the focal point of a number of

fault tolerant features

• Mechanical components are more susceptible to failure

than electronic components

• The hard disk is most vulnerable to failure in a server
• A number of fault tolerant features address the

possible failure of hard disks

Sever Based Implementation of Fault Tolerance

• Level 1
• Level 2
• Level 3

Preview of Fault Tolerance

• Based on the premise of maintaining multiple copies of critical components
• Level 1
  • Duplicate FATs
• Level 2
  • Duplicate server hard disks
• Level 3
  • Duplicate servers

Other Features

• Uninterruptible Power Supply (UPS)
• Tape backup

Uninterruptible Power Supply (UPS)

• Ensures the uninterruptible supply of power to the server
• Batteries in the UPS will continue to provide power in the event of a power outage

Tape Backup

• Used more as a precautionary measure than a fault

tolerant measure

• Data on the server is periodically backed up on a

tape

• If the disk storage fails on the server:
  • A previously stored version of the data is loaded on to a

newly installed disk storage on the server

• Offers some degree of protection against the total

loss of data

Network Operating System Support for Reliability

• Support for Levels 1 and 2 of fault tolerance is readily available in network operating systems
• Currently support is also available for Level 3 fault tolerance as well
• RAID 0,1 and 5 are commonly supported

MODULE

Level 1 Fault Tolerance

Level 1 Fault Tolerance

• A Software Based Solution