All about DATA backups & rotation


DATA backup is to make copies of particular data in order to use those copies for restoring the information if a failure occurs (a data loss event due to deletion, corruption, theft, viruses etc.).

there are four common backup types implemented and generally used in most of these programs: full backup, differential backup, incremental backup and mirror backup.


  • Full backup

Full back up is the starting point for all other types of backup and contains all the data in the folders and files that are selected to be backed up.


  • Differential backup

Differential backup contains all files that have changed since the last FULL backup. The advantage of a differential backup is that it shortens restore time compared to a full back up or an incremental backup.


  • Incremental backup

Incremental backup stores all files that have changed since the last FULL, DIFFERENTIAL OR INCREMENTAL backup. The advantage of an incremental backup is that it takes the least time to complete.


  • Mirror backup

Mirror backup is identical to a full backup, with the exception that the files are not compressed in zip files and they cannot be protected with a password. A mirror backup is most frequently used to create an exact copy of the source data.


  • Smart backup

Smart backup is a backup type which combines the full, differential and incremental backup types with cleanup operations in order to efficiently manage the backups according with the backup settings and the free disk space in destination. The Smart backup type starts with a full backup.

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Tape Rotation

A good tape rotation schedule is vital to ensure data recovery. The best rotation schedule is one that provides you with a long and varied history of file versions.

Grandfather-Father-Son Backup Scheme


This is the most commonly used media rotation schedule. This scheme uses daily (Son), weekly (Father), and monthly (Grandfather) backup sets. Four backups tapes are labeled for the day of the week each backs up.

Tower of Hanoi Backup Scheme


The Tower of Hanoi rotation schedule is widely used. In this schedule, one tape set “A” is used every other backup session (daily sessions in this example). Start Day 1 with “A” and repeat every other backup session (every other day). The next tape set “B” starts on the first non- “A” backup day and repeats every fourth backup session. Media set “C” starts on the first non-“A” or non- “B” backup day and repeats every eighth session. Media set “D” starts on the first non-“A”, non-“B”, or non-“C” backup day and repeats every sixteenth session. Media set “E” alternates with media set “D”.

What is ALE, ARO, SLE.?


Quantitative Risk Assessment

Quantitative assessment deals with numbers and dollar amounts. It attempts to assign a cost (monetary value) to the elements of risk assessment and to the assets and threats of a risk analysis.

To fully complete a quantitative risk assessment, all elements of the process (asset value, impact, threat frequency, safeguard effectiveness, safeguard costs, uncertainty, and probability) are quantified. Therein lies the problem with purely quantitative risk assessment: It is difficult, if not impossible, to assign dollar values to all elements; therefore, some qualitative measures must be applied to quantitative elements. A quantitative assessment requires substantial time and personnel resources. The quantitative assessment process involves the following three steps:

  1. Estimate potential losses (SLE)
  2. Conduct a threat analysis (ARO)
  3. Determine annual loss expectancy (ALE)

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Annual loss expectancy (ALE)

The expected value (cost) of a yearly occurrence of incidents of given type, in monetary units. It is a product of SLE and ARO (SLE*ARO). The ALE for each type of incident is different.


Annual rate of occurrence (ARO)

Expected number of an incident’s occurrences during a calendar year. For rare incidents, it is equivalent to a probability of one or more incidents during a year; for frequent incidents, it is equivalent to the expected number of incidents per year. The ARO for each type of incidents is different.

Gross margin

The difference between revenue and cost before accounting for certain other costs. Generally, it is calculated as the total selling price of the items sold (revenue), less the cost of goods sold (production or acquisition costs).


The term here used for all costs borne by the entity besides the personnel costs.

Revenue (also called turnover)

The annual sum of all net invoices issued by a company, i.e. the total net price (without VAT) of all products sold during the fiscal year.

Single loss of expectancy (SLE)

The expected value (cost) of an incident in monetary units, assuming its single occurrence. The SLE for each type of incidents is different.

Total ALE (TALE)

The total expected annual loss expectancy from all types of incidents considered.