The Backup Strategy Guide
1. Introduction to tape backups|
2. Tape rotation systems
3. Implementing a backup system
1. Introduction to tape backups
Data Backups - a necessary part of risk management
With the increasing risks of computer viruses, cyber-vandalism and hardware failure, implementing a systemized data backup plan is a necessary part of any business' strategy for risk management.
Data loss can occur because of a multitude of other reasons too, such as accidental file deletion, and may go undetected for days, weeks or longer. A good backup strategy needs to allow you to restore data from a variety of instances back in time.
Tape backups - the ideal medium
Tape is an ideal medium for backing up data because of its high storage capacities, low cost, and the ability to store cartridges off-site.
Organizing a number of tapes into an efficient backup library also allows you to restore data from different points in time, and archive data. This is further explained in Chapter 2.
A number of different tape formats exist. Some common formats include:
|Tape format||Data capacity (uncompressed)||Data transfer rate||Applications|
|Travan||1 - 20Gb||1Mb/sec||Home use, low range servers|
|DAT / DDS / 4mm (Digital Data Storage on Digital Audio Tape)||2 - 20Gb||2.75Mb/sec||Low range servers, small business|
|AIT (Advanced Intelligent Tape)||15 - 50Gb||3Mb/sec||Low to mid range servers|
|LTO (Linear Tape Open)||200 - 1600Gb||40-320Mb/sec||Mid to high range servers and mainframes|
The average small business and organization will find that a Travan or 4mm DDS tape will provide the solution in terms of data capacity and cost. All data will generally fit onto a single tape, meaning that a single stand-alone tape drive can be purchased (instead of more expensive options such as tape autoloaders, etc)
When should backups take place?
Backups should ideally take place outside of business hours, when network traffic is at its minimum. Scheduling the backup at some time during the night (eg. Midnight) is a suitable tactic for most organizations. Backing up data once a day (after each working day) provides good coverage against data disaster.
Different types of backups
Different types of backups are available in backup software. Each will backup different amounts of data, and different types of files as summaried below:
|Backup type||Files that are copied over to backup media|
|Full||All files, system data, etc.|
|Differential||All files added or changed since the last full backup|
|Incremental||All files added or changed since the last full, differential or incremental backup|
|Daily||All files added or changed on the day of the backup|
A Full backup will copy all files and system data to the backup media. It allows for the complete restore of all data from one single tape.
Differential, Incremental and Daily are partial backups are designed to reduce amount of data backed-up to the media, resulting in faster backups. To restore data using one of these backups, the last Full backup tape will also be required, along with any other partial backups since the last Full backup.
For example, if Full backups are performed on Mondays, and Incremental backups on the other days, to restore last Thursday's data, 4 tapes would be required (Monday full + Tuesday incremental + Wednesday incremental + Thursday incremental).
The problem with partial backups is the requirement for multiple tapes when restoring data. If any of these tapes is faulty, then the restore cannot be guaranteed to proceed correctly.
Clearly, if all your data can fit onto a single tape, performing full backups all the time is the safest strategy.
The backup tape rotation methods described in Chapter 2 can be implemented manually or in software.
One particular piece of software, BackupAssist (www.backupassist.com) is specifically designed to help small business owners in managing and scheduling their tape backups. It interacts with the Microsoft Windows Backup program to provide an easy way of implementing a tape rotation strategy easily.
More details on using backup software to assist your backup process are given in Chapter 3.