Vulnerability of data (Data Backup)
Abstract
Know about the purpose and value of backing up data, software to a removable
storage device.
Data is vulnerable in many ways:
The system on which it is stored can fail. For example, a hard drive may crash
due to component failure.
The medium itself may become corrupt. Where data is stored on a magnetic
medium, this can become corrupt due to a number of factors including
moisture, heat, magnetic fields and electromagnetic radiation. Even optical
storage which is highly reliable should never be regarded as infallible.
The system can be stolen.
The system could be physically damaged through war, criminal activity,
vandalism or carelessness.
The system could be damaged as a result of a natural disaster such as a flood,
fire or earthquake.
The data could be deleted or changed through criminal activity, vandalism or
carelessness.
No matter what care you may take to protect a system, additional copies of data need
to be made and stored on a regular basis. Copies of data are referred to as backups.
The following are some guidelines to working with backups.
Once backups have been created, they should be store in a secure area at a
different site. Never keep backups on the same site as the system. They could
be stolen or destroyed along with the rest of the system.
Backups should be made on a very regular basis. Even for a small
organisation, this should be done daily. Even the loss of a single day's work
would be a major problem. In large organisations backing up may take place
on an on-going basis. A schedule of backing up should be clear policy and
adhered to.
More than one copy of data should be made. If the data is very valuable, the
different copies could be stored in different secure locations.
Different versions of the backup should be retained. The following is an
example of a backup schedule that could be followed.
The cycle of backing up starts on the first Monday of the month. At the end of
each day of the week a backup is made. At the end of the week, there is a
Monday, Tuesday, Wednesday ... Saturday backup. On Sunday a backup is
created and labelled week 1 backup. This is kept for the rest of the month. The
weekday tapes are then reused and the process repeated. At the end of the
month you end up with a series of weekly backups. The last one becomes the
backup for the month and the process starts over the next month. At the end of
the year you then have a series of monthly backups.
An appropriate medium for backing up must be used. In the case of companies
this would generally be done using tape, although optical storage is becoming
more common. For personal use, a CD or DVD makes an excellent backup.
DVD writers are still quite expensive. Never use diskettes for backup
purposes. They are not reliable for this purpose. Even when backing up a PC,
makes multiple copies and keep them at another site for safe storage. You
could, for example, use a safety deposit box at a bank.
Often a network server has two identical hard drives, one being a mirror image of the
other. This means that if one fails the other one can take over. In other words all the
software on the first is identical to the software on the second.
Software can be backed up by making a copy of the cd/dvd media and then storing the
originals and using the backups to install from. This is allowed by most software
manufacturers. The original is kept under lock and key along with the licence
numbers.