The best Backup strategies

Various types of data backup are used as part of a backup strategy. Read on to explore an overview of the most common types. More detailed in­form­a­tion can be found in the articles linked below. A backup strategy usually includes periodic full backups as well as in­cre­ment­al or dif­fer­en­tial backups in between.

Here’s a brief overview of the three main types of backup and their strengths and weak­nesses, which we will consider in more depth below.

A low com­plex­ity of creation and recovery mean that the backups of this method can be created and restored with on-board means. If a method has a high com­plex­ity, special software is usually required. In principle, low com­plex­ity is prefer­able.

The volume of data generated when creating a backup in­flu­ences two di­men­sions:

1. Storage re­quire­ments of the backup medium: how much space is needed to create another backup?
2. Scope of transfers: backups are copies of data. The copied data must be read from the source, trans­ferred, and written to the des­tin­a­tion media. Large transfers require high bandwidth to complete in an ac­cept­able time frame.

Creating a backup takes a little time. This includes the time required for copying the data as well as any other upstream or down­stream steps. The time required depends on the com­plex­ity of the backup method, the resulting volume of data and the bandwidth available between the source and target system.

Creating backups is only one side of the coin. The effort involved is useless if the backups cannot be restored in the event of damage. In principle, in­de­pend­ent backups are prefer­able to linked backup chains, as this minimises the risk of data loss.

The term `backup´ is ubi­quit­ous in the in­form­a­tion age. But what exactly is a backup? The term existed before the wide­spread use of digital systems. In principle, a backup system is a provision for main­tain­ing op­er­a­tions in the event of an emergency. For example, a hospital has a backup generator. This stands in if the primary power supply fails.

In terms of digital systems, backups are re­dund­antly stored data. Simply put, copies of important data are created and dis­trib­uted across different media. If the main data storage device is damaged, the data can be re­con­struc­ted from one of the backups. Following the 3-2-1 backup rule, one of your backups should be in the cloud. Backups are par­tic­u­larly important in two cir­cum­stances:

1. Loss of data. Lost data can be re­con­struc­ted from the backup.

Digital systems are virtual. The smallest errors can lead to full data loss. Con­cep­tu­ally, this is like a sky­scraper col­lapsing when a single screw fails. Then the only thing that helps is to have a redundant copy available.

       2. Changing data. Data can be reset to a prior state.

Digital systems develop a “life of their own” as com­plex­ity increases. If un­in­ten­tion­al changes occur, they are often difficult or im­possible to reverse. This is because troubleshoot­ing and cor­rect­ing errors can consume a great deal of time and effort without guar­an­tee­ing a positive result. It is therefore better to restore the data from a pre­vi­ously created copy.

A backup strategy is needed to ensure that backups can be used in an emergency. After all, backups are only valuable if they are planned and created with foresight. A backup strategy includes the following basic con­sid­er­a­tions:

1. Which data must be backed up?
2. At what intervals?
3. On which media?
4. Using which methods?
5. How is the integrity of the backups ensured?
6. How are backups restored if necessary?

The final points tend to be often neglected. If it takes an emergency for you to notice that your backups don’t contain the desired data or are not suitable for restoring data, it’s already too late. Therefore, it’s important to ex­tens­ively test the entire process from creating backups to restoring them. A solid backup strategy ensures that there are no nasty surprises in the event of data loss.

There are several methods to create con­tinu­ous backups of a dataset. The three main backup methods  full backup, dif­fer­en­tial backup, and in­cre­ment­al backup each offer specific ad­vant­ages and dis­ad­vant­ages. In this article, we provide an overview of them, but you can read more about each type in our in-depth guides on each backup strategy.

Generally, a backup strategy usually includes several types of backups. First, a full backup is created. This is followed by in­cre­ment­al or dif­fer­en­tial backups and, if necessary, periodic full backups. Different data sets are backed up with varying frequency using the ap­pro­pri­ate methods, depending on re­quire­ments.

Let’s assume an or­gan­isa­tion has a current dataset of 100 GB in need of backing up. Let’s further assume that the dataset grows by 1 GB a day. As part of a con­ven­tion­al backup strategy, a full backup is created on the weekend. Fur­ther­more, daily amends are to be backed up by another backup. So all backup methods start with a full backup on Sunday. Sub­sequently, depending on the backup method, only changes are backed up if necessary.

Let’s compare the three types of data backup. First, we compare the size of daily growth in data with data volumes accruing per backup method. The volume of the full backups cor­res­ponds to the volume of the data stock. The volume of a dif­fer­en­tial backup grows linearly over time as of the last full backup. In contrast, the volume of in­cre­ment­al backups cor­res­ponds to the volume of data changed:

Creating backups is an important aspect of a backup strategy. But what about data recovery? The table below compares the types of backups by con­sid­er­ing the number of backups required to restore them. To restore full and dif­fer­en­tial backups, a constant number of backups are necessary for recovery. With in­cre­ment­al backups, the number of required backups grows linearly over time since the last full backup:

A full backup creates a complete copy of all data on a system. This can be a copy of all data on a laptop or, for example, a copy of all digital payrolls for the year. If several full backups of the same data are created at different times, there is usually a high level of re­dund­ancy in the data they contain. This is because most data only changes at certain points in time. A full backup serves as the basis for the two other types of backups.

Since a full backup covers the entire defined data stock, there is usually a high volume of data to be backed up. It follows that creating a full backup requires a lot of storage space on the backup medium. In addition, the process usually takes a long time. On a positive note, a full backup does not require much effort: you simply back up everything. Fur­ther­more, restoring data from a full backup is usually straight­for­ward.

A dif­fer­en­tial backup contains all of the data that has changed since the last full backup. The amount of data to be backed up depends on how much time passed between a dif­fer­en­tial backup and the last full backup. As a rule, however, a dif­fer­en­tial backup is much smaller and therefore faster to create than another full backup.

To restore data, the dif­fer­en­tial backup and the last full backup are required. If multiple dif­fer­en­tial backups are created, they are in­de­pend­ent of each other. If one dif­fer­en­tial backup becomes corrupted, other dif­fer­en­tial backups are not affected. Some common admin tools allow the creation of dif­fer­en­tial backups. For example, dif­fer­en­tial backups can be created with Rsync.

An in­cre­ment­al backup  backs up changes since the last full or in­cre­ment­al backup. The in­di­vidu­al backups are small and fast to create. However, in­cre­ment­al backups are not in­de­pend­ent of each other. Restoring them requires all in­cre­ment­al backups since the last full backup. If an in­cre­ment­al backup in the chain is damaged, all sub­sequent in­cre­ment­al backups are worthless.

Due to the small volume of data to be backed up, in­cre­ment­al backups are par­tic­u­larly efficient and therefore widely used. They tend to be used to create frequent backups of smaller changes. For example, in­cre­ment­al backups are useful to back up on a Mac via “Time Machine”. In­cre­ment­al backups on Windows 10 are easy with the Robocopy Backup tool.