Differential backup: the clever alternative

Backing up company-relevant and customer-specific data has long since become a business success criterion. In order to decide on a suitable form of backup for your company, you first need to be clear about which data needs to be backed up, how often and how much downtime you can afford in the worst case. If the backup is carried out differentially, even frequent changes to data can be reliably backed up within short periods of time.

@@What is a differential backup?

Differential data backup is a method in which changes are saved in relation to the last complete backup. This means that a complete backup is first saved on a data carrier. If changes are made shortly afterwards, these are backed up separately on another data carrier. If further adjustments are then made, all data that has changed since the last complete backup is saved in the same way.

A differential backup enables relevant data to be saved more quickly and can reliably back up a large number of data changes. However, a high level of storage capacity is required to implement such a differential backup, as all data already saved since the last full backup is also saved again with each new backup. A certain amount of data redundancy cannot be avoided.

Differentiation from other types of backup

The simplest form of backup is the full backup or complete backup. Here, all existing data is backed up at the end of each specified period, for example on the Friday of a week. The disadvantage here is the high storage capacity required and the correspondingly large amount of time required. In the event of a disaster, only the last backup would be required with this method. However, only this backup would be available.

A classic form of complete backup would also be the generation or grandfather-father-son principle. In this case, backups of all existing data are made at different times. If a downstream backup ("son") is lost, the lost data can be restored from the information in the upstream backup ("father"). In practice, this could mean that a full backup is created each day ("son"), which is overwritten with the current data on the following days of the coming week. On Friday, additional backups would be made of the entire week's events, which would not be overwritten ("father"). On the last day of the month, a complete backup of all data created in the month in question would also be carried out, which would also be stored separately ("grandfather"). After one month, the last weekly backup would be overwritten for the first time, and the monthly backup after one year. Data stored one year previously could thus be restored in the event of loss. Unlike a differential backup, a data backup based on the generation principle intentionally creates long-term redundancies. More storage capacity is required, which means more time is required.

@@Another data backup concept is incremental backup. Here, changes and adjustments are saved separately in shorter periods of time until the next complete backup. In terms of a week, this would mean that a full backup would be created at the weekend. Changes made on the following Monday would be backed up using a hard disk. Changes occurring on Tuesday would be saved again on another data carrier, and so on.

The differential data backup would save changes in a similar way, but without creating a separate backup for each day. On Monday, all changes made that day would be saved; on Tuesday, all changes made that day would be saved, including the changes already saved on Monday. On Wednesday, in addition to the Wednesday events, Monday and Tuesday would be saved again and so on until the end of the week. Whether a backup is performed incrementally or differentially depends on the importance and security classification of the data to be backed up. While the incremental method would require both the last full backup and all subsequently saved change backups, a differential backup would only require the last full backup and the last backup to enable the data to be restored. If you are looking for a specific file, it will also be quicker to find it on just 2 backups.

@@Consideration in the backup strategy of a company

A differential backup is particularly useful for companies that make frequent changes to their data and want to keep it safe at all times. The security classification of the data to be backed up must therefore be clearly defined. Such data could be order data, for example. It must also be clear how much space is available for storing the storage media and at what intervals the differential backup should take place (hourly, daily, weekly). It must also be clear when complete backups are to be carried out. Depending on the amount of data, a decision can be made as to whether a differential backup is the best solution.

Restoring a differential backup: How does this work?

If a differential backup is to be restored, the medium described with the differential backup must be compared with the last complete backup.

Differential backup on tapes: Does it make sense in the long term?

Large amounts of data of around 3-4 terabytes can be stored on magnetic tapes. If their integrity is checked regularly, they are very secure and take up little space. They are less susceptible to mechanical stress than hard disks, for example, but even tapes cannot withstand electromagnetic stress unscathed. After 5-6 years, the tapes must be re-stored in order to prevent adverse effects due to decreasing magnetization.

Differential backup to external hard disk

A differential backup should be saved on an external hard drive, for example, to prevent losses due to technical failures or access by unauthorized third parties. For smaller companies, it is also advisable to store backup media such as tapes and hard disks in safe deposit boxes or similar. Larger companies can also make use of specially secured rooms (cells).

Differential backup: handling the archive bit

A differential backup requires the data to be backed up to be marked with an archive bit. Such marking is carried out using a bit. The data to be backed up is marked with a tick (bit) by default, which initiates its backup. After the changed data has been backed up, the marking must be removed accordingly so that only edited data is saved when the next backup is performed.

@@@@Langmeier Backup: the right solution for every company

Are you looking for a reliable and uncomplicated form of data backup and the right software for your company? Langmeier offers various backup solutions for companies. The tools offered by Langmeier are equally suitable for RAID data backup, the creation of an EDP backup copy or a Microsoft backup. The business package is a suitable data backup option for large companies but is also interesting and usable as a backup solution for small companies. Whichever backup option you choose, Langmeier has a solution tailored to your company that will ensure your long-term success.