Backup Strategy Guide
The
Backup
Strategy
Guide
How to protect your
small business
from data disaster
COPYRIGHT
Copyright 2003 Cortex I.T. Pty. Ltd. All rights reserved. This document and information contained herein
are the property of Cortex I.T. Pty. Ltd. No part of this document may be reproduced, transmitted,
transcribed, stored in a retrieval system, or translated into any language or computer language in any form
or by any means, electronic, mechanical, magentic, optical, chemical, manual or otherwise, without the
express written permission of Cortex I.T. Pty. Ltd., 125 Middleborough Road Victoria 3128 Australia.
KEYWORDS AND PHRASES
backup rotation method, backup rotation scheme, backup rotation strategy, backup rotation system,
backup scheme, backup system, backup strategy, tape backup, tape backup library, tape backup for
small business, tape backup software, tape rotation method, tape rotation scheme, tape rotation strategy
TRADEMARKS
Microsoft, Windows, Seagate, Imation are registered trademarks. BackupAssist is a trademark of Cortex
I.T. Pty. Ltd. All other product names are trademarks or registered trademarks of their respective owners.
REVISION HISTORY
Revision
1.1
1.0
Date
November 2003
April 2003
Description
Minor updates
Initial release
CONTACTING CORTEX I.T.
Cortex I.T. Pty. Ltd.
125 Middleborough Road
Box Hill South, Victoria 3128
Australia
Tel: +61 4 1262 5071
Fax: +61 3 8080 1606
Cortex IT Home Page: www.cortexit.com
BackupAssist Home Page: www.backupassist.com
The Backup Strategy Guide
ii
Executive Summary
This manual provides an introduction to data backup strategies using tape, and provides an
overview of common tape rotation systems. The steps to implementing a backup strategy
are also provided.
This guide is aimed at the people responsible for protecting data in a small business – the
small business owner or system administrator.
Additional Resources
This guide should give you enough information to implement a backup system for your
small business or organization.
For more information on hardware, be sure to contact your local computer store or
technical support personnel.
For information on backup software, visit the following websites:
BackupAssist website – http://www.backupassist.com
Backup Strategies website – http://www.backupstrategy.info
Tape Backups website – http://www.tapebackups.info
The Backup Strategy Guide
iii
Table of Contents
1. INTRODUCTION TO TAPE BACKUPS..................................................................................................1
Data Backups – a necessary part of risk management............................................................................. 1
Tape backups – the ideal medium.......................................................................................................... 1
Tape formats........................................................................................................................................ 1
When should backups take place?......................................................................................................... 1
Different types of backups.................................................................................................................... 2
Backup Software.................................................................................................................................. 2
2. TAPE ROTATION SYSTEMS.................................................................................................................3
Five tape rotation – one per day.............................................................................................................3
Grandfather – Father – Son (GFS)......................................................................................................... 3
Tower of Hanoi.................................................................................................................................... 4
3. IMPLEMENTING A BACKUP SYSTEM.................................................................................................5
Pitfalls to avoid in a backup system....................................................................................................... 5
The 3 steps to implementing a backup system........................................................................................ 5
What level of investment is required?.................................................................................................... 6
What should I do now?......................................................................................................................... 6
The Backup Strategy Guide
iv
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.
Tape formats
A number of different tape formats exist. Some common formats include:
Data capacity1
Data transfer rate
1 - 20Gb
1Mb/sec
Home use, low range servers
DAT / DDS / 4mm (Digital Data 2 - 20Gb
Storage on Digital Audio Tape)
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
Tape format
Travan
Applications
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.
1
Typical uncompressed data capacities and data transfer rates are quoted
The Backup Strategy Guide
1
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.
Backup Software
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.
The Backup Strategy Guide
2
2. Tape Rotation Systems
In a tape rotation system, multiple tapes are organised into a tape backup pool, or tape
backup library to provide you with data recovery capabilities, whilst allowing for selected
backup tapes to be stored off-site for added security.
Different tapes are used for different days' backups according to a predefined system.
Three such tape rotation systems are described here.
Five tape rotation – one per day
The simplest tape rotation scheme is to have one tape for each day of the working week.
Tapes are labelled: Monday, Tuesday, Wednesday, Thursday, Friday.
For example, consider the calendar below:
Monday
Tuesday
1
Wednesday
2
Tuesday
7
8
Monday
14
Tuesday
Monday
21
Monday
Thursday
Wednesday
Tuesday
Friday
18
Thursday
24
Wednesday
Friday
11
17
23
29
Monday
Thursday
Wednesday
Tuesday
Friday
4
10
16
22
28
Wednesday
9
15
Thursday
3
Friday
25
Thursday
Friday
30
Tuesday
Wednesday
You can restore data from any one of the tapes in your library – or in this case, any day in
the past the week. This strategy requires only five tapes, but only provides one week's data
backup history.
Grandfather – Father – Son (GFS)
The grandfather – father – son schedule is the most widely used method, and involves
backing up data in the following way:
•
daily – on the “son tapes”
•
weekly – on the “father tapes”
•
monthly – on the “grandfather tapes”
This system is far more powerful than the five tape rotation, but requires more tapes.
The Backup Strategy Guide
3
For example, consider the calendar below:
Monday
Tuesday
1
Wednesday
2
Tuesday
7
8
Month 1
14
21
Week 3
Week 4
Thursday
Wednesday
Tuesday
Friday
11
17
23
29
Thursday
Wednesday
Tuesday
Friday
4
10
16
22
28
Wednesday
Tuesday
Week 2
3
9
15
Thursday
Friday
18
Thursday
24
Wednesday
Friday
25
Thursday
Friday
30
Tuesday
Wednesday
This strategy provides you with the ability to restore data from the last week, plus any
Monday over the last month, plus any month for as many monthly tapes as you have.
Variations on this scheme are available, and provide a trade-off between the number of
tapes required, and the number of monthly tapes available.
Tower of Hanoi
The Tower of Hanoi a complex strategy where five tapes are used – called A, B, C, D, E.
•
•
•
•
A is used every other day
B is used every 4th day
C is used every 8th day
D and E are used every 16th day, alternating
This ensures that data is available from the last day, 2 days ago, and three other times in
history. However, the range of history of backup is dependent on where one is in the cycle.
Consider the following calendar:
Monday
Tuesday
1
Wednesday
2
A
7
8
A
14
B
B
21
A
D
D
E
C
A
18
A
24
A
C
11
17
23
29
A
A
A
Friday
4
10
16
22
28
B
9
15
Thursday
3
B
25
B
A
30
A
B
This method is clearly confusing, but has the advantage of only requiring 5 tapes. Unless
aided by software, this method is not recommended because it is prone to human error.
The Backup Strategy Guide
4
3. Implementing a backup system
Pitfalls to avoid in a backup system
There are several pitfalls that can reduce the effectiveness of any tape backup system:
•
Faulty media – if you run the same tapes for years, eventually they will wear out.
However, your backup software should be able to detect faulty tapes when it verifies
the data written to the tape after each backup.
•
Human error – if you place the wrong tape in the tape drive for a backup, you'll
obviously disrupt the system. There are ways of minimizing human error, which
includes using software such as BackupAssist, to email your administrator/secretary
daily, and instruct him/her to place a certain tape in the drive.
•
Insecure storage of tapes – it is critical that your tapes be stored in a secure location
such as a fireproof safe, and that your monthly, quarterly and yearly tapes be stored off
site. Please note that if you store all your backup tapes next to your file server, and your
building gets robbed or burns down, not even the best tape backup library in the world
will get your data back.
The 3 steps to implementing a backup system
So now that you know the basic theory and options available, what's the fastest and most
cost effective way of protecting your data? Here are the 3 steps that I recommend my
clients:
Step 1 – select and purchase your backup hardware
The data of most small organizations will fit onto a single tape. Work out the amount of
data that you need to back up, and select an appropriate tape drive according to these rough
guidelines:
•
Up to 10 Gig – Travan cartridge drive
•
Up to 20 Gig – DDS tape backup drive
•
Up to 40 Gig – DDS tape backup drive with hardware data compression
Then purchase the necessary tapes for your backup rotation strategy. A good GrandfatherFather-Child variation will require 10 tapes or 14 tapes.
Step 2 – implement backup processes, using software
The next step is to select a tape rotation strategy, devise a calendar of tapes, and to set up
your tape backup software to schedule tape backups at the end of the working day. This
process is time consuming, but fortunately there is software available to simplify the
process.
The Backup Strategy Guide
5
I recommend BackupAssist (www.backupassist.com) for this purpose, as it provides a
simple, inexpensive way of implementing a backup strategy, thus saving time and money.
More details and a downloadable trial version can be found on the BackupAssist website.
Step 3 – continually perform your backups!
Backups must be done every working day to be effective.
And as obvious as this sounds, the correct tape should be placed in the drive. For example,
placing the “Week 2” tape instead of the “Week 3” tape in the tape drive will reduce the
effectiveness of your tape rotation strategy!
Software such as BackupAssist will email your administrator or secretary the correct tape
to place in the drive on any given day to minimise human error.
In addition, you should monitor the results of each backup to check for errors. For
example, if a tape wears out and data cannot be verified, you need to take action and
replace that tape.
By default, Windows Backup will not notify you of errors – it's a manual process of
opening up the backup logs and ensuring that the backup proceeded correcctly.
However, software such as BackupAssist will email you the backup logs daily, enabling
you to monitor the backup results without having to manually check them.
Be sure to also follow your manufacturer's guidelines for drive cleaning and maintenance.
What level of investment is required?
Your investment in data protection will not be insignificant, but is small when compared to
the costs associated with data loss.
The prices quoted (in US dollars) here are estimates of typical hardware, from the buy.com
website, at 10th April 2003. In the example, 15 tapes have been purchased to implement the
“Professional” data backup rotation scheme.
Item
Qty
Cost
Seagate Travan 20 Gig Drive (STT220000A-RDT)
1
$269.00
Imation 20Gb data cartridges (12118) 3 pack
5
$445.90
BackupAssist software
1
$129.00
Total investment
$843.90
What should I do now?
This guide should give you enough information to implement a backup system for your
small business or organization. For more information, consult the resources listed in the
Additional Resources section at the start of this manual.
The Backup Strategy Guide
6
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