1. McLean 20061 HIGHER COMPUTER NETWORKING Lesson 15 (a) Disaster Avoidance Description of disaster avoidance: use of anti-virus software use of fault tolerance components use of uninterrupted power supply. regular maintenance

2. McLean 20062 HIGHER COMPUTER NETWORKING What You Should Know About Avoiding Disaster Techniques include: use of anti-virus software use of fault tolerance components use of uninterrupted power supply regular maintenance Disaster Avoidance Many things can go wrong with a network.

3. McLean 20063 HIGHER COMPUTER NETWORKING What You Should Know About Avoiding Disaster Anti-virus software Up-to-date anti-virus software running on the server and its clients. Use of Fault Tolerance Components These ensure the system is able to recover after failure. Redundancy i.e. having more of a resource than is actually required so that if one fails you have another ready to take its place e.g. a server with a built-in dual power supply RAID (Redundant Array of Independent Discs) is where all data on one disc is automatically copied (mirrored) onto another or other discs. Clustering of servers is grouping servers to act as one – if one goes down another takes over its job.

4. McLean 20064 HIGHER COMPUTER NETWORKING What You Should Know About Avoiding Disaster Uninterrupted Power Supply UPS uses a battery which will provide between 15 and 20 minutes of reserve power in the event of a power cut. This allows network users to save work and close applications without serious loss of data. Regular Maintenance It is essential to have a preventative maintenance strategy. This involves regular inspection of all network components to try and anticipate any hardware failures before they happen.

5. McLean 20065 HIGHER COMPUTER NETWORKING Lesson 15 (b) Backup Description of backup strategy: backup server mirror disks tape backup schedule

6. McLean 20066 HIGHER COMPUTER NETWORKING What You Should Know About Network Backup Network Backup Strategy It is essential to have an effective backup strategy in place. All user files are usually backed up as applications and programs can be re-installed from CD. Backup Server A computer set aside for the purpose of backup which may use RAID technologies and mirror discs. Using a backup server as a central store eliminates the risk of important data being overlooked by the backup schedule.

7. McLean 20067 HIGHER COMPUTER NETWORKING What You Should Know About Network Backup Mirror Discs A mirror disc is a hard disc, or discs, which automatically store the exact contents of another disc. Mirror discs are ‘written to’ every time a user file is updated or added. Magnetic Tape DAT tape has a capacity of 8GB while Digital Linear Tape (DLT) has a capacity of up to 80GB with a transfer rate of 6MB per second. Super DLT has a capacity of up to 220GB with a transfer rate of up to 40MB per second.

8. McLean 20068 HIGHER COMPUTER NETWORKING What You Should Know About Network Backup Backup Schedule The backup schedule dictates when backups are made. Full Backup - Usually carried out on a weekly basis. All user files are backed up whether they have been updated or not so is a lengthy process. Differential Backup - Carried out at the end of every day where only user files that have been updated are backed up. This saves time and capacity. Incremental Backup - This where any files that have been changed since the last backup (of any type) are backed up. This is the fastest type of backup though data recovery can take more time.