Backup Strategy
HIGHER INFORMATION SYSTEMS
Backup Strategy
An Exam question will ask you to describe a backup strategy.
Be able to explain:
Safe, secure place in different location.
Why? – For disaster recovery.
Talk about rotation method – we will look at
Grandfather, Father, Son.
Need to know –
Archive,
Recovery
Storage methods
Frequency & Version Control
Rotation Method (Grandfather Father, Son)
Backup Strategy
Data can often be irreplaceable so a copy must be created
that is stored in a safe secure location away from the
original.
The media used for this will be:
•Tape (magnetic)
•External portable hard disks (plural, not just one disk)
The reason for a backup is to ensure that the most recent
copy of the data can be recovered and restored.
Backup Strategy
Causes:
Physical
Fire
Flood
Building collapse
Electronic
Corrupted hard disk
Files being Accidentally erased
Virus attack on a disk
Backup Strategy
Archive
Files that are not accessed often can be saved to tape for
long term storage. If required they can be accessed at a
later date. This frees up hard disk space. They are a
permanent copy - not to be used for recovery (it is the
backup that is used if there is a disaster).
Backup Strategy
Recovery
The most important thing to do once data has been backed
up is to ensure this has been successful.
When the data needs to be accessed it is brought from the
off-site location and the recovery software will restore the
data.
When you need to recover data that has been corrupted (or
accidently deleted) you would use the most recent (full)
backup as well as all the subsequent incremental backups.
Backup Strategy
Full backup
•Taken at a fixed time, e.g. once per day/per week. This
backs up everything including the data and the software
programs.
•Thereafter incremental backups (daily, weekly), this means
only files that have been amended since the last full or
incremental backup are backed up.
•Recovery software deals with this – it can be set to
full/incremental.
Backup Strategy
Storage Methods:
Media:
•Magnetic tapes – DAT tapes
•Multiple hard drives using USB
connections.
•Stored in a fire-proof safe
•Stored off site away from the original
Backup Strategy
Frequency and Version Control
Frequency:
A backup has to be completed by the start of business
the next morning.
A full backup is done on a Friday or Saturday night. This
is done automatically so the operator does not have to
be present.
Incremental backups are done each evening. (A backup
should be done at least once per day).
Backup Strategy
Frequency and Version Control
Version:
This is the full backup plus incremental tapes made up
throughout the week.
They must be labelled clearly and kept together.
A set of these tapes in the G,F,S rotation method is
known as a generation.
E.g. If the system was corrupted on Wednesday to fully
restore the data you would need the full backup (done on
Friday night) plus the incremental tapes. It depends on
how this is done but you must end up with all the data
restored to the system.
Backup Strategy
Grandfather, Father, Son
The cost or time required to do a full backup everyday can be
impractical. Many users therefore will do either an incremental or
differential backup most days. (An incremental backup is a backup of
every file on a file system which has changed since the last backup.)
Differential Backs up every file that has changed since the last full
backup is backed up each time.
It is faster to restore a differential backup.
All you need is the last full and last differential backup.
http://www.techfaq.com/incremental
-backup.shtml
Backup Strategy
Grandfather, Father, Son
Incremental
Backups back only the files that have changed since the last full or
incremental backup are backed up.
Subsequent incremental backups only back up those files that have
changed since the previous incremental backup.
It takes longer to restore data since data from the last full backup,
plus data from all the incremental backups, must be restored.
Grandfather-Father-Son
The most commonly used media rotation schedule is
"Grandfather-Father-Son" (GFS). This scheme uses daily
(Son), weekly (Father), and monthly (Grandfather) backup
sets.
Son – each day of the week
Father - at the end of each week
Grandfather - last day of the
month
Annual Grandfather-Father-Son. Under this scheme the “Son” group of
media consists of four backup media are labelled for the day of the week
each backs up; for example, Monday to Thursday. The “Father” group of
media consists of a set of four weekly backup media is labelled "Week1,"
"Week2," and so on.
The "Grandfather" media consists of a set of full backups on the last business
day of each month of the year and an archive copy which is removed
offsite.
Backup Strategy
We have learned:
Safe, secure place in different location.
Why? – For disaster recovery.
Causes - Physical or Electronic
Archive
Recovery
Storage methods
Frequency & Version Control
Rotation method –Grandfather, Father, Son.
Question
2008 Q17
Lachlan is preparing for an interview for the job of network security manager
at First Place Ltd. The company has 4 warehouses supplying 40 branches
throughout the country. As stock control system is used to manage daily
supplies to each branch. As part of the interview he will be asked about a
security strategy for the company’s organisational information system.
(b) Describe a suitable backup strategy for First Place Ltd. Your answer should
describe:
•
A storage method
•
A recovery method
•
A rotation method
(5)