What is georedundancy?

The term georedundancy describes the use of two data centers at remote locations that have the same data status and can take over the function of the other at any time. The physical distance is supposed to prevent failures due to disasters, storms, and accidents and other factors.

Table of Contents

• Georedundancy definition
• For which companies is georedundancy relevant?
• What are the BSI guidelines on georedundancy?
• How does the Open Telekom Cloud help companies comply with the BSI's georedundancy recommendations?

Companies and government agencies that depend on the constant availability of their IT systems use so-called redundancy data centers as part of disaster recovery strategy. These provide the same server functions as the main data centers and serve to relieve the load as well as to prevent failures. 

Georedundancy is the term used when these redundant data centers are set up with a large spatial distance between them to prevent both from failing due to a cross-regional event such as floods, earthquakes or a chemical or nuclear accident.

In Germany, georedundancy is particularly important for companies that operate so-called critical infrastructures (Kritis), for example energy providers, banks, or healthcare companies. The IT Security Act (IT-SiG) requires them to secure their IT in accordance with the "state of the art". Among other things, it requires the establishment of an appropriate information security management system. How this is to be implemented is documented in the requirements of the Federal Office for Information Security (BSI). Every two years, every Kritis company must have its security standard checked by an independent body and report its weak points to the BSI. 

The BSI recommends two georedundant sites if data centers of availability category 3 or higher are required to operate the respective critical infrastructure. These must be available at least 99.99% of the time. In other words, they must not be down for more than 5 minutes per month or 53 minutes per year.

According to the BSI definition, critical infrastructures are operated by companies from the following sectors:

• Energy
• Health
• Government and administration
• Food
• Transportation and traffic
• Finance and insurance
• Information and Telecommunications
• Media and Culture
• Water

Of course, not every bakery is immediately a critical infrastructure just because it operates in the food sector. The federal authorities have regulated which systems are included in the "Ordinance for the Determination of Critical Infrastructures". For example, only facilities that produce or handle more than 434,500 tons of food per year are considered critical. Only the systems required to operate the critical infrastructure are affected by the BSI's recommendations. 

To meet the specific requirements of the affected industries, industry associations develop industry-specific security standards (B3S), which are approved by the German Federal Office for Information Security (BSI). 

In 2019, the German Federal Office for Information Security (BSI) redefined the minimum distance between data centers with a new edition of the "Criteria for the siting of highly available and georedundant data centers". The distance was increased from 5 to 200 kilometers.

The BSI justifies this with the "defense against forces of nature" such as the 2005 snowstorm in Münsterland or the Elbe and Danube floods in 2013. These events made it clear that entire areas can be affected by such major damage events.

At the same time, the BSI is aware that the greater distance between data centers also leads to higher latencies in data transmission. It therefore allows the distance to be reduced to up to 100 kilometers in individual cases if rapid and constant synchronization of data is considered more important for operational security. However, it requires companies to make this decision on the basis of a risk analysis and to justify it in detail in writing.

In addition to physical distance, the BSI specifies other characteristics that must be met before a data center pair can be designated as georedundant:

• Flooding
  Two georedundant data centers must not be located near the same river system. In this context, a river system is a main river with all its tributaries. For example, the Rhine as the main river forms a river system with the Moselle, Neckar and Main as tributaries. An exception applies if the data center is located five meters above the mark of the highest flood since 1960.
• Earthquakes
  A maximum of one data center may be located in an earthquake zone, which may not exceed category 1. This means that with a probability of 90 percent, no earthquake greater than magnitude 7 on the Richter scale will occur within 50 years. In Germany, the earthquake zones run from the Black Forest along the Rhine and along the Danube to Regensburg. There are also earthquake zones in the western Ore Mountains, in the Alps and in the "Cologne Bay" between Cologne and Aachen.
• Wind
  Only one data center may be located in a category 4 wind load zone. In Germany, these are only found along the coasts of the North and Baltic Seas.
• Power supply
  Only one of the georedundant data centers should be located within a grid segment of the highest voltage of 220 or 380 kilovolts – the so-called maximum voltage used to transport electricity over long distances.
• Staff
  Operators should plan staffing to ensure that sufficient qualified personnel are always available. For pandemic preparedness, they need to consider which employees with which qualifications are required on site and which  can do their work remotely. If a catering company is feeding employees at both data centers, they need to ensure that they are not preparing food in the same kitchen.

The Open Telekom Cloud offers companies an easy way to comply with the BSI recommendations. Its data centers are spread across two regions – Germany and the Netherlands. The sites in each region have three availability zones, i.e. physically separate data centers. There are more than 500 kilometers between the German and Dutch branches of the Open Telekom Cloud – more than enough to meet the BSI recommendations. Telekom has also carefully selected them. For example, the areas around the data centers in Magdeburg, Biere and Amsterdam are earthquake-proof. There are also no settlements, flight paths or highways in the direct vicinity. In addition, they are located in different flood protection zones. 

These georedundant data centers mirror the resources of the Open Telekom Cloud as needed. In this way, servers, storage and customer data would be available even if natural forces such as earthquakes or floods were to cause outages at one location. You can find more information on our data center overview page.