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Backup Type
Data Only vs. Complete Operating System and Data Backup
The determination of a complete data plus operating system
backup is somewhat dependent on the environment.
Complete operating system failures typically don’t happen as
often as data failures. Operating systems also don’t
typically change as often as the data.
Catastrophic operating system failures are often caused by
hardware errors, and if specific hardware needs to be
replaced, it is often the case more than not, that a
complete re-installation of the operating system may need to
be done anyway.
As part of a backup strategy, it may only be worthwhile to
backup the operating system periodically such as on a weekly
basis.
Complete System Backup vs. Partial
When practical, the most prudent backup strategy is to
perform a complete system backup every working day.
If there are 22 working days in the month, 22 tapes should
be used for the daily backups whenever possible.
This insures the ability to recovery any file for at least
one month.
Furthermore, if weekly and monthly processing is performed,
a partial backup should be performed of the transaction
files before processing and then a full backup after the
period has been processed.
Keep 5 weekly tapes and 13 monthly tapes.
When disaster strikes and a critical data volume is lost,
being able to restore the entire volume from last night's
backup reduces the liability of attempting to restore the
volume from multiple incremental and base line backups.
If you are performing full backups every night and last
night's backup failed, and a critical data volume is lost
before the next backup, then the volume can be restored from
the backup created the night before (and so on).
As a standard rule, do not append to tapes without just
cause. Prudent disaster recovery planning conflicts with the
practice of leaving a tape in the drive and using it all
week. The last five backups are all resident on just one
extremely thin strand of tape.
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