The Perennial Conflict between Availability and Consistency


Prof. Dr.-Ing. David Bermbach developed interest in his current specialty in his first semester of industrial engineering at the Karlsruhe Institute of Technology (KIT). “At the time, programming was actually the only hands-on subject in which you could do your own thing and didn’t just have to learn theory. That kind of put me on this track,” explains the 33-year-old, Mainz-born industrial engineer, who has headed Mobile Cloud Computing at TU Berlin since December 2017. Mobile Cloud Computing also forms part of the Einstein Center Digital Future (ECDF).

For his doctoral thesis for Prof. Dr. Stefan Tai, then still at KIT, Bermbach was already looking at data management and application architecture in geo-distributed systems, especially their quality features. Additionally, his goal was and is not only to make the quality features of such systems, such as consistency and performance, measurable but to directly influence these as well. These topics are highly charged, and not just for companies such as Amazon and Google. “In principle, every Dropbox user is familiar with the issue: if two people change the information in a Dropbox at the same time and then save, there are then two versions of the information that can no longer be automatically merged. These inconsistencies are the result of ‘trade-offs’ between the availability and the consistency of information. On the one hand, data should always be available everywhere; on the other hand, they have to be updated globally at the same time. You can now scale the problem and, for example, look at the server of a large bank that needs to update its applications. One server is in the United States, another in Germany, and another, for instance, in Singapore; seconds can go by until all servers have been updated. In this time, there could be transactions that would lead to different account details on different servers for the same account. In individual cases, this could have significant consequences,” Bermbach explains.

What Bermbach, who plays saxophone and composes, especially likes about the ECDF is that all ECDF professors are encouraged to seek and foster contact to each other and, above all, outside their own departments. “Since it is simply expected that we attend particular events or guide particular processes, networking really does take place. I am hopeful that this will lend a new quality to exchange that generates new, interesting ideas.”